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Apples are one of the most important economic crops worldwide. Because of global warming and an aggravation of environmental, abnormally high temperatures occur frequently in fruit-growing season and seriously affect normal fruit growth and reduce fruit quality and yield. We took five-year-old 'Ruixue' (Qinfu 1 x Pink Lady; CNA20151469.1) fruits as test materials, and the ambient temperature during fruit development was monitored. The results showed that during the fruit-growing season, especially during the rapid growth stage (July to August), the maximum daily temperature exceeded 30 °C and lasted for more than 40 days. To determine the effects of high temperature stress on the apple fruit resistance, we treated expanding, veraison, and maturity-period fruits at different temperatures. It was found that the fruits of the expanding period showed strong resistance to high temperature stress, whereas during veraison and maturity, fruit resistance to high temperature stress decreased, and the fruit peel browning phenotype appeared. Meanwhile, the content of malonaldehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion (...) in the peel gradually increased with increasing temperature. The content of total phenols, flavanol, and flavonoids in the peel decreased substantially at 45 #176;C. Moreover, it was found that polyphenol oxidase gene (MdPPO1) was most sensitive to high temperature stress in apple. Furthermore, transient and stable MdPPO1 overexpression significantly promoted peel browning. The transgenic materials were more sensitive to high temperatures, and browning was more severe compared to non-genetically modified organism (WT). Stable MdPPO1 knockout calli obtained via clustered regularly interspersed short palindromic repeats (CRISPR/Cas9) gene knockout technology reduced the browning phenotype, and the resultant fruits were not sensitive to the effects of high temperature stress. Thus, MdPPO1 expression may be a key factor of high temperatureerelated changes observed in the browning phenotype that provides a scientific theoretical basis for the selection of high temperatureeresistant varieties and apple cultivation and management in the future. [ABSTRACT FROM AUTHOR]

This article examines the morphological characteristics of apple varieties in northeastern Algeria, specifically focusing on the leaves, fruits, and terminal shoots of three apple varieties: Golden Delicious, Royal Gala, and Starkrimson. The study reveals limited morphological diversity among the investigated apple cultivars, with some descriptors showing insignificant differences between cultivar types. The findings emphasize the distinct physiological and morphological characteristics of each variety and highlight the need for further exploration and conservation efforts. Another document provides information on the application rate of sheep manure and urea for soil salinity levels, as well as the physical and chemical analysis of soil in an orchard. It also discusses the growth habit and length of annual shoots for different apple tree varieties, as well as the flowering characteristics and fruit characteristics such as weight, length, width, shape, color, and ripening period. The document is valuable for understanding the cultivation and quality of apple trees in the studied orchard. Lastly, a document discusses the characterization of new apple cultivars and their implications for sustainable development and consumption. The study found significant variation in vegetative growth, fruit weight, and color among the three cultivated apple tree varieties examined. The authors suggest further research and evaluation to fully understand the genetic diversity and potential uses of these cultivars, emphasizing the importance of rigorous protocols for measurement and observation. The document includes a list of references for further reading on apple diversity and characterization. [Extracted from the article]

Adventitious root formation is a bottleneck during vegetative proliferation. Potassium (Kþ) is an essential macronutrient for plants. Kþ accumulation from the soil and its distribution to the different plant organs is mediated by Kþ transporters named Kþ transporter (KT), Kþ uptake (KUP), or high-affinity Kþ (HAK). This study aimed to identify members of the HAK gene family in apples and to characterize the effects of Kþ supply on adventitious root formation and on the expression of HAK genes and the genes that putatively control auxin transport, signaling, and cell fate during adventitious root formation. In this study, 34 HAK genes (MdHAKs) were identified in the apple (Malus x domestica 'Golden Delicious') genome. A phylogenetic analysis divided MdHAKs into four clusters (I, II, III, and IV), comprising 16, 1, 4, and 13 genes, respectively. The syntenic relationships revealed that 62.5% of the total MdHAK genes arise from genomic duplication events. Chromosome location, domain structure, motif analysis, and physico-chemical characteristics were subsequently investigated. Furthermore, the application of Kþ indicated the emergence of adventitious roots at 8 d and produced more adventitious roots at 16 d than the Kþ-free control (CK) treatment. In addition, various MdHAKs showed root-specific expression in B9 apple rootstock stem cuttings and enhanced expression during the initiation and emergence stages of adventitious root formation in response to Kþ treatment. Additionally, Kþ treatment enhanced the expression levels of MdPIN1, MdPIN2, and MdAUX1. Further data indicated that a higher expression of MdWOX11, MdLBD16, and MdLBD29 and of cell cycle-related genes contributed to the auxin-stimulated adventitious root formation in response to Kþ. [ABSTRACT FROM AUTHOR]

The regulation of apple (Malus domestica) fruit texture during ripening is complex and a fundamental determinant of its commercial quality. In climacteric fruit, ripening-related processes are regulated by ethylene (ET), and jasmonate (JA) is also involved in the ethylene biosynthesis pathway, mainly through the transcription factor MYC2. However, the molecular genetic mechanism for fruit ripening processes between the JA and ET signaling pathways still needs to be elucidated. In order to explore how JA regulates apple fruit ripening through ERF4, we used 'Gala' and 'Ralls Janet' fruit at different developmental stages as experimental materials to determine the fruit firmness and related gene expression analysis. Meanwhile, we carried out different hormone treatments on 'Gala' fruit at ripening stage. Here, we show that ERF4 is a core JA signaling hub protein JASMONATE ZIM-DOMAIN (JAZ) interactor that affects ethylene signaling pathways. During fruit development, ERF4 represses the expression of ACS1 and ACO1 by interacting with JAZ, as well as with the JA-activated transcription factor MYC2. Ripening is promoted in JAZ-suppressed apples. Thus, ERF4 acts as a molecular link between ethylene and JA hormone signals, and the natural variation of the ERF4 Ethylene-responsive binding factor-associated amphiphilic repression (EAR) motif decreases repression of ethylene biosynthesis genes. [ABSTRACT FROM AUTHOR]

Recently, four quantitative trait loci linked to flesh mealiness in apples were identified, with one associated with the MdPG1 allele. Hence, this study analyzed cell wall changes in two mealy (Orin and Akane) and three nonmealy (Kiou, Kitaro, Fuji) apple cultivars during ripening. The fruits were harvested for each cultivar at optimum maturity and stored at 20°C for 20 days. The flesh firmness of 'Kitaro' and 'Fuji' fruit did not change strikingly over the 20 days, whereas that of the other three cultivars, especially 'Akane' and 'Orin', gradually decreased during ripening. Between the two cultivars with a mealy texture, 'Akane' fruit produced extremely low levels of ethylene, whereas 'Orin' fruit produced high levels. The watersoluble polyuronide (WSP) contents of 'Kiou' and 'Fuji' fruit did not change clearly. In contrast, the WSP contents of the other three cultivars, especially 'Akane' and 'Orin', increased during ripening. In 'Kiou', 'Kitaro', and 'Fuji' fruit, the molecularmass distributions of WSPs did not change during ripening. Conversely, the molecularmass distribution of WSPs in 'Akane' and 'Orin' fruit exhibited downshifts during ripening. These results indicate that solubilization and depolymerization of pectic polyuronides occur during ripening in mealy 'Akane' and 'Orin' fruit, and that ethylene may not be involved in these changes. [ABSTRACT FROM AUTHOR]

Apple is widely cultivated in temperate regions. The beneficial properties of apple for preventing several illnesses are widely known. Nevertheless, qualitative variables such as sweetness or sourness may influence consumer satisfaction; they are critical factors for fruit consumption and essential in plant breeding. In the present work, 155 apple accessions were assessed during five consecutive years (2014–2018). Four individual sugars and seven organic acids were analysed by HPLC. A mixed-effects model was fitted with accessions and the years' climatic features as independent variables. A cluster analysis was applied on the mixed-effects model coefficients. Four groups were considered as optimum. Genetics seemed to have the strongest effect and showed clear differences between accession groups, while climate effects were strong only for certain compounds and had a more horizontal behaviour equally affecting the different accession groups. In fact, non-Spanish cultivars tended to concentrate, while autochthone accessions had a much wider spread. Individual sugars and acids concentrations correlated negatively with precipitation and positively with temperature range and solar radiation in all accession groups. The geographic region where the orchard is grown is thus very important in the resulting metabolites profiles. Moreover, apple genetics would also play a decisive role as highlighted in the cluster analysis. [ABSTRACT FROM AUTHOR]

Though grafting in plants is in practice since ages only limited information is available on the graft-induced morphological, biochemical and molecular variations. The mechanism(s) by which rootstocks influence scion vegetative growth and development, and vice versa, are not fully understood. Therefore, in the present investigation, we studied graftinduced variations in different apple stionic combinations using scion (Scarlet Gala and Red Fuji) and rootstocks (MM111, MM106, M7, M9 and M26). Under morphological variations, significant difference was found in all the parameters viz. leaf area, shoot length, internodal length and fruit characters except petiole length and fruit firmness. Likewise, significant difference was also observed in the subjected stionic combinations based on total phenolic contents, total free amino acids and peroxidase enzyme activity. These results were further validated using DNA based molecular markers SSR. However, no polymorphism was observed in both the stionic combinations at DNA level. These results imply that rootstocks may influence morphological and biochemical parameter of the scion during graft-union but it does not influence genetic constitution of scion at DNA level. Further studies at RNA or protein level are required to unravel the reasons behind these variations. [ABSTRACT FROM AUTHOR]

Haplotypes provide useful information for genomics-based approaches, genomic prediction, and genome-wide association study. As a small number of superior founders have contributed largely to the breeding history of fruit trees, the information of founder haplotypes may be relevant for performing the genomics-based approaches in these plants. In this study, we proposed a method to estimate 14 haplotypes from 7 founders and automatically trace the haplotypes forward to apple parental (185 varieties) and breeding (659 F1 individuals from 16 full-sib families) populations based on 11,786 single-nucleotide polymorphisms, by combining multiple algorithms. Overall, 92% of the single-nucleotide polymorphisms information in the parental and breeding populations was characterized by the 14 founder haplotypes. The use of founder haplotype information improved the accuracy of genomic prediction in 7 traits and the resolution of genome-wide association study in 13 out of 27 fruit quality traits analyzed in this study. We also visualized the significant propagation of the founder haplotype with the largest genetic effect in genome-wide association study over the pedigree tree of the parental population. These results suggest that the information of founder haplotypes can be useful for not only genetic improvement of fruit quality traits in apples but also for understanding the selection history of founder haplotypes in the breeding program of Japanese apple varieties. [ABSTRACT FROM AUTHOR]

Fruit shape is the result of the interaction between genetic, epigenetic, environmental factors and stochastic processes. As a core biological descriptor both for taxonomy and horticulture, the point atwhich shape stability is reached becomes paramount in apple cultivar identification, and authentication in commerce. Twelve apple cultivars were sampled at regular intervals from anthesis to harvest over two growing seasons. Linear and geometric morphometrics were analysed to establish if and when shape stabilised and whether fruit asymmetry influenced this. Shape stability was detected in seven cultivars, four asymmetric and three symmetric. The remaining five did not stabilise. Shape stability, as defined here, is cultivar-dependent, andwhen it occurs, it is late in the growing season. Geometric morphometrics detected stability more readily than linear, especially in symmetric cultivars. Key shape features are important in apple marketing, giving the distinctness and apparent uniformity between cultivars expected at point of sale. [ABSTRACT FROM AUTHOR]

The apple (Malus domestica) is one of the world's most commercially important perennial crops and its improvement has been the focus of human effort for thousands of years. Here, we genetically characterise over 1000 apple accessions from the United States Department of Agriculture (USDA) germplasm collection using over 30,000 single-nucleotide polymorphisms (SNPs). We confirm the close genetic relationship between modern apple cultivars and their primary progenitor species, Malus sieversii from Central Asia, and find that cider apples derive more of their ancestry from the European crabapple, Malus sylvestris, than do dessert apples. We determine that most of the USDA collection is a large complex pedigree: over half of the collection is interconnected by a series of first-degree relationships. In addition, 15% of the accessions have a first-degree relationship with one of the top 8 cultivars produced in the USA. With the exception of 'Honeycrisp', the top 8 cultivars are interconnected to each other via pedigree relationships. The cultivars 'Golden Delicious' and 'Red Delicious' were found to have over 60 first-degree relatives, consistent with their repeated use by apple breeders. We detected a signature of intense selection for red skin and provide evidence that breeders also selected for increased firmness. Our results suggest that Americans are eating apples largely from a single family tree and that the apple's future improvement will benefit from increased exploitation of its tremendous natural genetic diversity. [ABSTRACT FROM AUTHOR]

A rising proportion of the world population suffers from food-related allergies, including incompatibilities to apples. Although several allergenic proteins have been found in apples, the most important proteins that cause allergic reactions to apples in Central-Northern Europe, and North America are the Mal d 1 proteins, which are homologues of the birch pollen allergen Bet v 1. As the demand for hypoallergenic fruits is constantly increasing, we selected apple genotypes with a low total content of Mal d 1 by enzyme-linked immunosorbent assay analysis from segregating populations and tested the tolerability of these fruits through a human provocation study. This tiered approach, which exploited the natural diversity of apples, led to the identification of fruits, which were tolerated by allergic patients. In addition, we found a significant correlation (coefficient >0.76) between the total Mal d 1 content and flavan-3-ol amount and show that the isoform composition of the Mal d 1 proteins, which was determined by LC-MS/MS has a decisive effect on the tolerability of apple genotypes. The approach presented can be applied to other types of fruit and to other allergenic proteins. Therefore, the strategy can be used to reduce the allergen content of other plant foods, thereby improving food safety for allergy subjects. [ABSTRACT FROM AUTHOR]

Societal Impact Statement: The English West Country is the home of cider making, providing the region with jobs and industry, as well as cultural reference points such as Laurie Lee's Cider with Rosie. Many important cider apple varieties were developed at Long Ashton Research Station (LARS), near Bristol, UK, including 29 varieties known collectively as 'The Girls'. After its closure, some of the knowledge and expertise acquired at Long Ashton was lost, including the pedigree of 'The Girls'. We sampled LARS' derived trees and, using a novel genotyping technique, rediscovered the pedigree of 'The Girls', ensuring that this important cider apple collection will be available for future generations. SummaryOur research had two objectives: (a) record the influence of Long Ashton Research Station on the introduction of new cider apple cultivars to the UK; (b) rediscover the parentage of the cider apple cultivars known collectively as 'The Girls'.For rapid, cost effective and accurate genotyping, we used the recently developed, medium density, single nucleotide polymorphism‐based genotyping procedure, SEQSNP®, to characterize the cultivars.We generated a medium density (1,500 markers), whole genome genotype for 245 apple cultivars that allowed us to determine the relationship between cultivars and, in so doing, rediscover the parentage of 'The Girls'.We show that SNP genotyping is an efficient tool for the analysis of genetic diversity in cider apples and apples in general, and that the cider apple breeding programme carried out at Long Ashton Research Station made, and continues to make, a unique contribution to UK cider production. [ABSTRACT FROM AUTHOR]

The leading condition for increasing the intensification of fruit and berry production is the improvement of the assortment of fruit crops and the realization of the genetic potential of cultivars. The role of the cultivar in determining the productivity level in horticulture is especially significant, due to the fact that fruit crops are perennial plants, enter fruiting for 4-7 years, on seedling rootstocks for 6-7 years. Replacing a cultivar that does not meet modern requirements with a new more intensive one requires a significant investment of time and money. The existing assortment of fruits used in Kazakhstan today does not fully meet the requirements of intensification. Improving the efficiency of production and gross harvests of Aport fruits based on the selection of selected forms, rootstocks, optimization of growing technology and determining the potential for laying port gardens in the region. Field, laboratory methods were used. The results of research on the study of zoned and promising apple varieties grown potentially ready for fruiting seedlings, optimization of planting density and improvement of the systems of formation, pruning of tree crowns, drip irrigation regimes in adaptive unsupported apple orchards on the Zhetysu-5 clonal rootstock are presented. The traditional cultivar Aport comes into fruiting for 8-10 years after laying the garden, while the varieties of modern selection (Golden Delishes, Sarkrimson, Zarya Alatau and others) provide full fruiting for 3-5 years. Moreover, Aport has a very pronounced fruiting frequency, i.e. after a good harvest the next year, Aport "rests." Aport is not resistant to disease. The fruits of Aport in vaults of the usual type are characterized by unsatisfactory keeping quality. The complex of the listed objective and subjective reasons has led to the fact that commodity producers began to prefer intensive varieties that provide a faster return on investment. Thus, our studies have shown that the fruits of the Aport cultivar from dwarf trees during the longterm storage period in fruit storages acquire higher palatability as compared to apples from trees on vigorous seedling rootstock. At the same time, in the first case, ascorbic acid is destroyed faster in fruits. The physiological disease "Jonathan spotting" and "tanning" are more susceptible to fruits from vigorous trees, browning of the pulp and the core of fruits, various fungal diseases - fruits from dwarf trees. Therefore, fruits for long-term storage must be laid separately, taking into account the growth power of trees depending on rootstocks, and earlier to realize fruits from dwarf trees. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cisgenic plants must be free of exogenous genetic elements such as antibiotic or herbicide resistance genes commonly used in the selection phase of a gene transfer protocol. However, the use of a selection marker is essential for the transformation of many fruit crops, including apple (Malus × domestica), for which the efficiency of DNA integration is very low. Currently, the approach with the highest chances of success relies on the removal of undesired exogenous genes by means of an inducible site-specific recombinase enzyme and its recognition sites. We developed a quantitative, rapid and cost-effective method based on real-time PCR to quantify the copy number of nptII marker gene in apple lines and to evaluate its elimination after the activation of the recombinase system. MdTOPO6 gene was chosen as endogenous reference gene for apple due to the single-copy presence in the haploid genome and to the species-specificity. A recombinant plasmid harboring specific sequences of both the reference gene and the target gene nptII was used as calibrator to build the standard curves. The limit of quantification of the method was evaluated, and precision and trueness of the quantification performances proved to be valid according to international reference criteria. Finally, this method was applied to characterize transgenic and cisgenic apple lines, and to investigate the possibility of removing an entire T-DNA cassette from the genome of edited apple plants. [ABSTRACT FROM AUTHOR]

Highlights • We selected flesh or peel samples in fruit different development stages of six cultivars in this study. • The expression of candidate reference genes WD40 , ACT and GAPDH were most stable in four peel samples. • The expression of candidate reference genes EF-1α , CKL and WD40 were most stable in two flesh samples. • The expression of candidate reference gene MDH was least stable among six flesh and peel samples. Abstract Apple (Malus domestica), as one of world's significant fruits, color of fruit contributes a lot for its high economic benefits and edible values. Quantitative real-time polymerase chain reaction (qRT-PCR) is a technique in molecular biology commonly used for the analysis of gene expression. Actually, stability of reference genes used in data normalization affects the accuracy and reliability of qRT-PCR to a large extend. Therefore, the present study was designed to identify and validate the suitable reference genes during the fruit development. We evaluated the stability of 10 candidate reference genes in peel or flesh samples of six cultivars during different development conditions. The qRT-PCR results showed that amplification efficiency of all candidate genes ranged from 95 to 111.3%. Three software packages geNorm, NormFinder, and BestKeeper recommended different reference genes in one same sample sets. So, an online tool RefFinder was applied for integrating above three results and then these 10 reference genes were ranked comprehensively. According to RefFinder, for all fruit development conditions, WD40 , ACT and GAPDH were identified as the most reliable reference genes for apple peel; EF-1α , CKL and WD40 for apple flesh, and MDH was the least stable reference gene for both samples. And, the expression patterns of target gene MdUFGT also validated this result. Further, we validated the suggested combination of different genes. Through the selection and validation of these internal reference genes, the accuracy and reliability of gene expression analysis in apple fruit tissues can be improved. [ABSTRACT FROM AUTHOR]

Abstract The UDP-glycosyltransferase UGT88F subfamily has been described first in Malus x domestica with the characterization of UGT88F1. Up to now UGT88F1 was one of the most active UGT glycosylating dihydrochalcones in vitro. The involvement of UGT88F1 in phloridzin (phloretin 2′- O -glucoside) synthesis, the main apple tree dihydrochalcone, was further confirmed in planta. Since the characterization of UGT88F1, this new UGT subfamily has been poorly studied probably because it seemed restricted to Maloideae. In the present study, we investigate the apple tree genome to identify and biochemically characterize the whole UGT88F subfamily. The apple tree genome contains five full-length UGT8 8F genes out of which three newly identified members (UGT88F6, UGT88F7 and UGT88F8) and a pseudogene. These genes are organized into two genomic clusters resulting from the recent global genomic duplication event in the apple tree. We show that recombinant UGT88F8 protein specifically glycosylates phloretin in the 2′OH position to synthetize phloridzin in vitro and was therefore named UDP-glucose: phloretin 2′- O -glycosyltransferase. The Km values of UGT88F8 are 7.72 μM and 10.84 μM for phloretin and UDP-glucose respectively and are in the same range as UGT88F1 catalytic parameters thus constituting two isoforms. Co-expression patterns of both UGT88F1 and UGT88F8 argue for a redundant function in phloridzin biosynthesis in planta. Contrastingly, recombinant UGT88F6 protein is able to glycosylate in vitro a wide range of flavonoids including flavonols, flavones, flavanones, chalcones and dihydrochalcones, although flavonols are the preferred substrates, e.g. Km value for kaempferol is 2.1 μM. Depending on the flavonoid, glycosylation occurs at least on the 3-OH and 7-OH positions. Therefore UGT88F6 corresponds to an UDP-glucose: flavonoid 3/7- O -glycosyltransferase. Finally, a molecular modeling study highlights a very high substitution rate of residues in the acceptor binding pocket between UGT88F8 and UGT88F6 which is responsible for the enzymes divergence in substrate and regiospecificity, despite an overall high protein homology. Graphical abstract Image 1 Highlights • The apple tree genome contains five UGT88F genes. • UGT88F8 is an UDP-glucose: phloretin 2′-O-glycosyltransferase. • UGT88F6 is an UDP-glucose: flavonoid 3/7-O-glycosyltransferase. [ABSTRACT FROM AUTHOR]

Malus sylvestris (L.) Mill, the European wild apple, is a small tree native to Europe which reaches its north-western limit in Northern Britain. It has been identified as one of the main contributors to the domesticated apple M. domestica (Suckow) Borkh. There are concerns that wild populations of this rare tree are threatened by hybridization with M. domestica throughout Europe. We genotyped 332 trees collected in the wild from Scotland and Northern England using 14 microsatellite markers to investigate levels of introgression in wild M. sylvestris populations. Our results showed that 70 per cent of the samples could be considered pure M. sylvestris, 27 per cent showed varying degrees of introgression from M. domestica and 3 per cent were pure M. domestica. Hybrids were more frequent in areas with more intensive land use and less semi-natural woodland. About 80 per cent of hybrids were identified as backcrosses to M. sylvestris. Areas in the Southern Highlands had the highest frequency of pure M. sylvestris trees (87 per cent). Morphological characters such as leaf size and hairiness as well as fruit size generally used by botanists for identification of M. sylvestris in the field proved to be unreliable as only 68 per cent of the trees could be identified accurately. Given the use of wild apple trees it seems likely that many of the trees collected from agricultural areas are planted and not the product of natural in situ hybridization and seed dispersal events thus compounding natural hybridization rates. Areas with high frequencies of pure M. sylvestris trees should be prioritized for conservation and possible measures are discussed to safeguard M. sylvestris as a species in Northern Britain. [ABSTRACT FROM AUTHOR]

Background: Somatic embryogenesis receptor-like kinases (SERKs) are leucine-rich repeat receptor-like kinases associated with various signaling pathways. These kinases have a relationship with stress signals, and they are also believed to be important for regulating plant growth. However, information about this protein family in apple is limited. Results: Twelve apple SERK genes distributed across eight chromosomes were identified. These genes clustered into three distinct groups in a phylogenetic analysis. All of the encoded proteins contained typical SERK domains. The chromosomal locations, gene/protein structures, synteny, promoter sequences, protein–protein interactions, and physicochemical characteristics of MdSERK genes were analyzed. Bioinformatics analyses demonstrated that gene duplications have likely contributed to the expansion and evolution of SERK genes in the apple genome. Six homologs of SERK genes were identified between apple and Arabidopsis. Quantitative real-time PCR analyses revealed that the MdSERK genes showed different expression patterns in various tissues. Eight MdSERK genes were responsive to stress signals, such as methyl jasmonate, salicylic acid, abscisic acid, and salt (NaCl). The application of exogenous brassinosteroid and auxin increased the growth and endogenous hormone contents of Malus hupehensis seedlings. The expression levels of seven MdSERK genes were significantly upregulated by brassinosteroid and auxin. In addition, several MdSERK genes showed higher expression levels in standard trees of 'Nagafu 2' (CF)/CF than in dwarf trees of CF/'Malling 9' (M.9), and in CF than in the spur-type bud mutation "Yanfu 6" (YF). Conclusion: This study represents the first comprehensive investigation of the apple SERK gene family. These data indicate that apple SERKs may function in adaptation to adverse environmental conditions and may also play roles in controlling apple tree growth. [ABSTRACT FROM AUTHOR]

Although gibberellin (GA) has been reported to control branching, little is known about how GA mediates signals regulating the outgrowth of axillary buds (ABs). In the current study, the effect of the exogenous application of 5.0 mM GA3 on ABs outgrowth on 1-year-old ‘Nagafu No. 2’/T337/M. robusta Rehd. apple trees was investigated and compared to the bud-activating treatments, 5 mM BA or decapitation. Additionally, the expression of genes related to bud-regulating signals and sucrose levels in ABs was examined. Results indicated that GA3 did not promote ABs’ outgrowth, nor down-regulate the expression of branching repressors [MdTCP40, MdTCP33, and MdTCP16 (homologs of BRANCHED1 and BRC2)], which were significantly inhibited by the BA and decapitation treatments. MdSBP12 and MdSBP18, the putative transcriptional activators of these genes, which are expressed at lower levels in BA-treated and decapitated buds, were up-regulated in the GA3 treatment in comparison to the BA treatment. Additionally, GA3 did not up-regulate the expression of CK response- and auxin transport-related genes, which were immediately induced by the BA treatment. In addition, GA3 also up-regulated the expression of several Tre6P biosynthesis genes and reduced sucrose levels in ABs. Sucrose levels, however, were still higher than what was observed in BA-treated buds, indicating that sucrose may not be limiting in GA3-controlled AB outgrowth. Although GA3 promoted cell division, it was not sufficient to induce AB outgrowth. Conclusively, some branching-inhibiting genes and bud-regulating hormones are associated with the inability of GA3 to activate AB outgrowth. [ABSTRACT FROM AUTHOR]

The present paper summarized some knowledge of modern technologies, applied in apple (Malus domestica) genome studies. New generation sequencing allowed single nucleotide polymorphism (SNP) chip technologies for genotyping, description of functional apple genes, characterization of the evolutionary results in apple genome fragment transition, as well as phylogenetic reconstruction of the genus Malus, being the confirmed progeny of M. sieviersii. Based on these technologies, newly developed putative markers may give the most important biological data such as age, geographical origins, tissue type determination, and external visible characters. The new generation genotyping platforms, representing very high efficiency, are now successfully applied for random apple genome-wide association (GWA) studies as well pedigree-based analysis and marker-assisted selection (MAS). [ABSTRACT FROM AUTHOR]

Relations between the apple cortex viscoelastic properties, water dynamics, histological, and chemical characteristics were investigated. Water mobility in four apple genotypes was studied by low-field NMR relaxometry prior and after plasmolysis of the cortex tissue. A discrete and a continuous method for decomposing the multi-exponential T 2 curves were implemented and compared. The results show that both methods of relaxation curve decomposition had close ability to discriminate genotypes before and after plasmolysis. Although the sensitivity of T 2 relaxometry allowed distinguishing microstructures among genotypes even after cellular fluids were mixed and diffused in plasmolyzed tissues, no relaxation component correlated with apple viscoelasticiy. Galactose and arabinose cell wall content were correlated with the storage modulus (E′) prior and after plasmolysis though the correlation signs were opposite and pointed to a potential key role of pectin RGI side chains in regulating apple texture in turgid tissue. [ABSTRACT FROM AUTHOR]

Abstract Tyrosine aminotransferase (TAT, EC 2.6.1.5) is the first key enzyme that catalyzes the reversible interconversion of tyrosine and 4-hydroxyphenylpyruvate in the tyrosine-derived pathway for syntheses of important secondary metabolites and compounds. Although plant TAT genes have been proposed to be important in response to abiotic stress, there is little information about TAT genes in woody perennial tree species, especially in economic fruit trees. Based on TAT domain searching, sequence homology screening and phylogenetic analysis, we identified four TAT s in apple genome. Then, we carried out a detailed phylogenetic analysis of TAT genes from multi-species, focusing on apple (Malus domestica). The result showed that the TAT family comprises three major classes corresponding to genes from angiosperms, mammals, and bacteria. Angiosperm TAT genes could be further divided into six subclasses. Analysis of intron-exon structure revealed that the typical TAT gene contains six introns and seven exons, with exons of similar size at each exon location. Promoter analysis showed that the 5′-flanking region of apple MdTAT s contain multiple cis -acting elements including those implicated in light, biotic stress, abiotic stress, and hormone response. MdTAT s were expressed to various levels in all apple structures and organs evaluated, and showed distinct expression patterns under water deficit stress. Ectopic expression of MdTAT2 in Arabidopsis or over-expression of MdTAT2 in apple callus tissue conferred enhanced tolerance to drought and osmotic stress. Collectively, these results suggest a role for TAT genes in drought and osmotic stresses and provide valuable information for further research of TAT genes and their function in plants. Highlights • Four MdTATs were identified in apple genome. • MdTATs might play important roles in responses to environments. • MdTATs showed distinct expression patterns in different apple tissues or under drought stress. • MdTAT2 overexpression increased resistance to drought and osmotic stress. [ABSTRACT FROM AUTHOR]

Copyright of Acta Alimentaria is the property of Akademiai Kiado and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: The FK506-binding proteins (FKBPs) play diverse roles in numerous critical processes for plant growth, development, and abiotic stress responses. However, the FKBP gene family in the important fruit crop apple (Malus × domestica Borkh.) has not been studied as thoroughly as in other species. Our research objective was to investigate the mechanisms by which apple FKBPs enable apple plants to tolerate the effects of abiotic stresses. Results: Using bioinformatics-based methods, RT-PCR, and qRT-PCR technologies, we identified 38 FKBP genes and cloned 16 of them in the apple genome. The phylogenetic analysis revealed three major groups within that family. The results from sequence alignments, 3-D structures, phylogenetics, and analyses of conserved domains indicated that apple FKBPs are highly and structurally conserved. Furthermore, genomics structure analysis showed that those genes are also highly and structurally conserved in several other species. Comprehensive qRT-PCR analysis found various expression patterns for MdFKBPs in different tissues and in plant responses to water-deficit and salt stresses. Based on the results from interaction network and co-expression analyses, we determined that the pairing in the MdFKBP62a/MdFKBP65a/b-mediated network is involved in water-deficit and salt-stress signaling, both of which are uniformly up-regulated through interactions with heat shock proteins in apple. Conclusions: These results provide new insight for further study of FKBP genes and their functions in abiotic stress response and multiple metabolic and physiological processes in apple. [ABSTRACT FROM AUTHOR]

Young ‘Nagafu No. 2′ apple trees produce fewer flower buds than the trees of other apple cultivars, including ‘Yanfu No. 6′ (i.e., ‘Fuji’ apple tree exhibiting a bud mutation). Thus, we analyzed the flowering characteristics of these two varieties to further characterize apple floral transition. RNA sequencing was used to characterize differentially expressed genes in buds between the two cultivars during floral transition. Differences in several physiological parameters were also analysed. A total of 3,010, 1,139, and 1346 differentially expressed genes were identified at 30, 50, and 70 days after full bloom. These genes combined with the differences in physiological indices indicated that low gibberellic acid levels and high cytokinin levels in ‘Yanfu No. 6′ buds during the floral induction stage increased the production of flower buds. High cytokinin levels inhibited gibberellic acid signaling and promoted floral transition. Additionally, low gibberellic acid levels likely inhibited shoot elongation by impairing DELLA degradation. Meanwhile, relatively high indole-3-acetic acid and cytokinin levels synergistically maintained meristem activities and accelerated bud growth. Moreover, the high sucrose content in ‘Yanfu No. 6′ buds up-regulated the transcription of TREHALOSE 6-PHOSPHATE SYNTHASE and SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE genes, which ultimately promoted floral induction. The data presented herein indicate that floral transition differences between the two analyzed apple cultivars are linked to sugar and cytokinin signaling pathways. [ABSTRACT FROM AUTHOR]

Recent studies with Arabidopsis and soybean have shown that a class of valine-glutamine (VQ) motif-containing proteins interacts with some WRKY transcription factors. However, little is known about the evolution, structures, and functions of those proteins in apple. Here, we examined their features and identified 49 apple VQ genes. Our evolutional analysis revealed that the proteins could be clustered into nine groups together with their homologues in 33 species. Historically, the main characteristics of proteins in Groups I, V, VI, VII, IX, and X were thought to have been generated before the monocot-dicot split, whereas those in Groups II, III + IV, and VIII were generated after that split. In the structural analysis, apple MdVQ proteins appeared to bind only with Group I and IIc MdWRKY proteins. Meanwhile, MdVQ1, MdVQ10, MdVQ15, and MdVQ36 interacted with multiple MdVQ proteins to form heterodimers but MdVQ15 formed a homodimer. The functional analysis indicated that overexpression of some apple MdVQ s in Arabidopsis and tobacco plants effected their vegetative and reproductive growth. These results provide important information about the characteristics of apple MdVQ genes and can serve as a solid foundation for further studies about the role of WRKY-VQ interactions in regulating apple developmental and defense mechanisms. [ABSTRACT FROM AUTHOR]

Antioxidant enzymes were well-known for reactive oxygen scavenging and protecting cells from oxidative damage in multiple biotic and abiotic stresses. Aimed to overview of antioxidant enzyme gene families and screen for drought and low-temperature response members, the whole apple antioxidant enzyme genes in apple genome were studied. Out of 73candidates in seven antioxidant enzyme gene families among the entire apple genome, a total of 49 genes were identified, showed more antioxidant enzyme gene members than those in other plant species. A phylogenetic tree based on predicted functional domains and motifs of apple and Arabidopsis antioxidant enzymes revealed 19 putative drought or low-temperature response genes, and 9 out 19 genes belong to five families responded to both drought and low-temperature stresses. Subsequently, cis-elements in those nine antioxidant enzyme gene promoters were examined and abundant elements involved in multiple hormone regulation and abiotic stresses response, including drought and low-temperature were found. The tissue expression specificity for those nine members in eight kinds of tissues was also examined. Screening and identifying both drought and low-temperature response genes provide useful information to understand gene functions and promote application of antioxidant enzyme genes in apple abiotic resistance breeding. [ABSTRACT FROM AUTHOR]

Some horticultural characteristics and bioactive contents of some local apple genotypes grown in Bolu province located in western black sea region were investigated. Along with the horticultural characteristics (fruit weight, width etc.), the phenolic spectrum and organic acids as bioactive content were determined. Among major phenolic compounds, catechin, chlorgenic acid, gallic acid, phloridzin and ratine content varied between 10.84- 5.16 mg 100 ml-1; 25.16-7.17 mg 100 ml-1; 7.35- 1.42 mg 100 ml-1; 6.12-1.18 mg 100 ml-1 and 5.16-1.01 mg 100 ml-1, respectively. The dominant organic acids were malic acid and fumaric acid among the organic acids. When the apple genotypes were evaluated overall in terms of horticultural properties and bioctive contents; it is suggested that 14BL02, 14BL09, 14BL06 and 14BL01 genotypes displayed superior properties and they may create a significant genetic resource to be use them in breeding activities in apple in future. [ABSTRACT FROM AUTHOR]

Simple sequence repeat (SSRs) markers derived from Malus were used to assess their transferability in the analysis of the genetic diversity and relationship of some Pyrus species. All studied microsatellite loci produced fragments and were polymorphic among the studied samples. Fifty-one allelic variants were detected at eight SSR loci, ranging from five (MS14h03, CH02b10 and CH03g06) to nine (CH02h11a), with a mean of 6.37 alleles per locus. A relatively high level of diversity was recorded among the studied accessions. The average of Shannon's index (I) was 1.04. The Dice genetic similarity coefficient ranged greatly and ‘Khoj 1’ (a member of P. communis) and ‘Shinko’ (a cultivar belonging to P. pyrifolia) had the lowest (0.21) values, while ‘Chojuro’ and ‘Nijisseiki’, two cultivars belonging to P. pyrifolia, had the highest genetic similarity (0.97) among the studied samples. Bayesian cluster analysis and principal coordinates analysis plot separated the P. pyrifolia samples from other species, and formed three distinct groups, indicating high genetic differences between P. pyrifolia and other studied pear species. Several private alleles were observed in some of the studied species that would be of great importance for species identification. Furthermore, in 23 samples, more than two alleles were observed in the CH04e03 locus, indicating presence of locus duplication in these samples. Our observations suggest that, for this locus, at least two homologous chromosomes or genomic regions may be presented in the genome of some pear samples. [ABSTRACT FROM AUTHOR]

Calyx-end cracking in 'Pink Lady' apple is treated by a solution of gibberellic acids 4 and 7 (GA 4+7 ) and the cytokinin 6-benzyladenine (BA). Although the GA 4+7 and BA mixture is applied early in apple fruit development, it mitigates cracking that becomes evident in the mature fruit, implying a long-term treatment effect. The reduced incidence of peel cracking is associated with increased epidermal cell density, which is maintained until fruit maturation. Presently, the expression of genes that have been previously reported to be associated with epidermal cell patterning and cuticle formation, or cracking resistance, was monitored in the peel during fruit development and following GA 4+7 and BA treatment. For most of the genes whose expression is naturally upregulated during fruit development, the early GA 4+7 and BA treatment maintained or further increased the high expression level in the mature peel. Where the expression of a gene was downregulated during development, no change was detected in the treated mature peel. Gene-networking analysis supported the interaction between gene clusters of cell-wall synthesis, cuticle formation and GA signaling. Overall, the data suggested that the GA 4+7 and BA treatment did not modify developmental cues, but promoted or enhanced the innate developmental program. [ABSTRACT FROM AUTHOR]

As a classic plant-specific transcription factor family - the Dof domain proteins - are involved in a variety of biological processes in organisms ranging from unicellular Chlamydomonas to higher plants. However, there are limited reports of MdDof (Malus domestica Borkh. DNA-binding One Zinc Finger) domain proteins in fruit trees, especially in apple. In this study we identified 54 putative Dof transcription factors in the apple genome. We analysed the gene structures, protein motifs, and chromosome locations of each of the MdDof genes. Next, we characterised all 54 MdDofs their expression patterns under different abiotic and biotic stress conditions. It was found that MdDof6,26 not only played an important role in the biotic/abiotic stress but may also be involved in many molecular functions. Further, both in flower development and pollen tube growth it was found that the relative expression of MdDof24 increased rapidly, also with gene ontology analysis it was indicated that MdDof24 was involved in the chemical reaction and flower development pathways. Taken together, our results provide useful clues as to the function of MdDof genes in apple and serve as a reference for studies of Dof zinc finger genes in other plants. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Apple gene, MD09G1111800, was identified as a chitin binding receptor-like kinase based on sequence similarity to AtCERK1 (chitin elicitor receptor kinase 1) from Arabidopsis. Sequence analysis on genomic structure, domain composition and transcriptional response to exogenous chitin treatment indicated that MD09G1111800 is an ortholog to AtCERK1 and was therefore named as MdCERK1 . Tissue specific expression patterns indicated that MdCERK1 is primarily functional in vegetative tissues of leaf and root, rather than flower, fruit and seed of apple plant. The transcriptional regulation patterns in response to infection by Rhizoctonia solani demonstrated that MdCERK1 is a functional pattern recognition receptor protein (PRR) in apple root tissues. The ability of purified GST-MdCERK1 fusion protein to bind chitin molecules added biochemical evidence for its role in chitin mediated immune responses. An untargeted proteomic approach was also employed for identifying its putative in vivo interaction partners in apple root cells, and results indicated the existence of a functional receptor complex. These data support the conclusion that MdCERK1 is a chitin binding receptor kinase functioning in apple vegetative tissues, which plays an important role in defense activation in response to pathogen infection. [ABSTRACT FROM AUTHOR]

Apple mosaic virus (ApMV) and prune dwarf virus (PDV) are amongst the most common viruses infecting Prunus species worldwide but their incidence and genetic diversity in Australia is not known. In a survey of 127 Prunus tree samples collected from five states in Australia, ApMV and PDV occurred in 4 (3%) and 13 (10%) of the trees respectively. High-throughput sequencing (HTS) of amplicons from partial conserved regions of RNA1, RNA2, and RNA3, encoding the methyltransferase (MT), RNA-dependent RNA polymerase (RdRp), and the coat protein (CP) genes respectively, of ApMV and PDV was used to determine the genetic diversity of the Australian isolates of each virus. Phylogenetic comparison of Australian ApMV and PDV amplicon HTS variants and full length genomes of both viruses with isolates occurring in other countries identified genetic strains of each virus occurring in Australia. A single Australian Prunus infecting ApMV genetic strain was identified as all ApMV isolates sequence variants formed a single phylogenetic group in each of RNA1, RNA2, and RNA3. Two Australian PDV genetic strains were identified based on the combination of observed phylogenetic groups in each of RNA1, RNA2, and RNA3 and one Prunus tree had both strains. The accuracy of amplicon sequence variants phylogenetic analysis based on segments of each virus RNA were confirmed by phylogenetic analysis of full length genome sequences of Australian ApMV and PDV isolates and all published ApMV and PDV genomes from other countries. [ABSTRACT FROM AUTHOR]

A new single-stranded positive-sense RNA virus, which shares the highest nucleotide (nt) sequence identity of 53.4% with the genome sequence of cherry-associated luteovirus South Korean isolate (ChALV-SK, genus Luteovirus), was discovered in this work. It is provisionally named apple-associated luteovirus (AaLV). The complete genome sequence of AaLV comprises 5,890 nt and contains eight open reading frames (ORFs), in a very similar arrangement that is typical of members of the genus Luteovirus. When compared with other members of the family Luteoviridae, ORF1 of AaLV was found to encompass another ORF, ORF1a, which encodes a putative 32.9-kDa protein. The ORF1-ORF2 region (RNA-dependent RNA polymerase, RdRP) showed the greatest amino acid (aa) sequence identity (59.7%) to that of cherry-associated luteovirus Czech Republic isolate (ChALV-CZ, genus Luteovirus). The results of genome sequence comparisons and phylogenetic analysis, suggest that AaLV should be a member of a novel species in the genus Luteovirus. To our knowledge, it is the sixth member of the genus Luteovirus reported to naturally infect rosaceous plants. [ABSTRACT FROM AUTHOR]

Malus hupehensis seedlings were treated with exogenous applications of IBA (0.1 mg L −1 and 0.5 mg L −1 ) in order to investigate the mechanism by which IBA promotes and effects lateral root (LR) development. Root morphology, plant height, plant crown diameter, and endogenous levels of hormone in LRs were evaluated. Additionally, patterns of differential gene expression related to root development were examined by RT-qPCR in IBA-treated and untreated roots during LR development. Results indicated that IBA treatment promoted both root and shoot growth, and that 0.5 mg L −1 IBA had a more obvious effect on growth promotion than 0.1 mg L −1 IBA. IBA treatment also induced an increase in the levels of endogenous auxin (IAA), zeatin-riboside (ZR), and the ratios of IAA/ABA and ABA/GA 1+3 , however, reduced gibberellin (GA 1+3 ) and abscisic acid (ABA) levels. In addition, there was also a significant upregulation in the expression of MdYUCCA4 , MdPIN1 , MdPIN2 and MdAUX1 in response to the IBA treatment; thus leading to an increase in auxin levels. Although MdIAA23 was induced, the expression of MdIAA5 and MdIAA14 , a negative regulator of MdARF7 and MdARF19 , were downregulated in IBA-treated apple seedlings. This resulted in elevated expression of MdARRO1 , MdGATA1 and MdSCR1, which was associated with an increase in lateral root development. Additionally, higher levels of endogenous auxin elevated the expression of MdWOX11 , and thus the expression of MdWOX5 , MdLBD16 and MdLBD29 ; collectively resulting in enhanced expression of the cell cycle related gene: MdCYCD3;1 . This pattern of expression was again associated with a promotion in lateral root development. In summary, changes in gene expression and hormone levels resulted in an increased number of LRs and other root growth parameters in IBA-treated plants. [ABSTRACT FROM AUTHOR]

Galactinol synthase (GolS) is a key enzyme in the biosynthetic pathway of raffinose family oligosaccharides (RFOs), which play roles in carbon storage, signal transduction, and osmoprotection. The present work assessed the evolutionary history of GolS genes across the Rosaceae using several bioinformatic tools. Apple (Malus × domestica) GolS genes were transcriptionally characterized during bud dormancy, in parallel with galactinol and raffinose measurements. Additionally, MdGolS2, a candidate to regulate seasonal galactinol and RFO content during apple bud dormancy, was functionally characterized in Arabidopsis. Evolutionary analyses revealed that whole genome duplications have driven GolS gene evolution and diversification in Rosaceae speciation. The strong purifying selection identified in duplicated GolS genes suggests that differential gene expression might define gene function better than protein structure. Interestingly, MdGolS2 was differentially expressed during bud dormancy, concomitantly with the highest galactinol and raffinose levels. One of the intrinsic adaptive features of bud dormancy is limited availability of free water; therefore, we generated transgenic Arabidopsis plants expressing MdGolS2. They showed higher galactinol and raffinose contents and increased tolerance to water deficit. Our results suggest that MdGolS2 is the major GolS responsible for RFO accumulation during apple dormancy, and these carbohydrates help to protect dormant buds against limited water supply. [ABSTRACT FROM AUTHOR]

Summary: Cytosine methylation is an essential feature of epigenetic regulation and is involved in various biological processes. Although cytosine methylation has been analysed at the genomic scale for several plant species, there is a general lack of understanding of the dynamics of global and genic DNA methylation in plants growing in environments challenged with biotic and abiotic stresses. In this study, we mapped cytosine methylation at single‐base resolution in the genome of commercial apple (Malus x domestica), and analysed changes in methylation patterns associated with water deficit in representative drought‐sensitive and drought‐tolerant cultivars. We found that the apple genome exhibits ~54%, ~38% and ~8.5% methylation at CG, CHG and CHH sequence contexts, respectively. We additionally documented changes in gene expression associated with water deficit in an attempt to link methylation and gene expression changes. Global methylation and transcription analysis revealed that promoter‐unmethylated genes showed higher expression levels than promoter‐methylated genes. Gene body methylation appears to be positively correlated with gene expression. Water deficit stress was associated with changes in methylation at a multitude of genes, including those encoding transcription factors (TFs) and transposable elements (TEs). These results present a methylome map of the apple genome and reveal widespread DNA methylation alterations in response to water deficit stress. These data will be helpful for understanding potential linkages between DNA methylation and gene expression in plants growing in natural environments and challenged with abiotic and biotic stresses. [ABSTRACT FROM AUTHOR]

Carotenoid cleavage oxygenases (CCOs) are able to cleave carotenoids to produce apocarotenoids and their derivatives, which are important for plant growth and development. In this study, 21 apple CCO genes were identified and divided into six groups based on their phylogenetic relationships. We further characterized the apple CCO genes in terms of chromosomal distribution, structure and the presence of cis -elements in the promoter. We also predicted the cellular localization of the encoded proteins. An analysis of the synteny within the apple genome revealed that tandem, segmental, and whole-genome duplication events likely contributed to the expansion of the apple carotenoid oxygenase gene family. An additional integrated synteny analysis identified orthologous carotenoid oxygenase genes between apple and Arabidopsis thaliana , which served as references for the functional analysis of the apple CCO genes. The net photosynthetic rate, transpiration rate, and stomatal conductance of leaves decreased, while leaf stomatal density increased under drought and saline conditions. Tissue-specific gene expression analyses revealed diverse spatiotemporal expression patterns. Finally, hormone and abiotic stress treatments indicated that many apple CCO genes are responsive to various phytohormones as well as drought and salinity stresses. The genome-wide identification of apple CCO genes and the analyses of their expression patterns described herein may provide a solid foundation for future studies examining the regulation and functions of this gene family. [ABSTRACT FROM AUTHOR]

As a family of transcription factors, DNA binding with one figure (Dof) proteins play important roles in various biological processes in plants. Here, a total of 60 putative apple ( Malus domestica ) Dof genes ( MdDof ) were identified and mapped to different chromosomes. Chromosomal distribution and synteny analysis indicated that the expansion of the MdDof genes came primarily from segmental and duplication events, and from whole genome duplication, which lead to more Dof members in apples than in other plants. All 60 MdDof genes were classified into thirteen groups, according to multiple sequence alignment and the phylogenetic tree constructed of Dof genes from apple, peach ( Prunus persica ), Arabidopsis and rice. Within each group, the members shared a similar exon/intron and motif compositions, although the sizes of the MdDof genes and encoding proteins were quite different. Several Dof genes from the apple and peach were identified to be homologues based on their close synteny relationship, which suggested that these genes bear similar functions. Half of the MdDof genes were randomly selected to determine their responses to different stresses. The majority of MdDof genes were quite sensitive to PEG, NaCl, cold and exogenous ABA treatment. Our results suggested that Md Dof family members may play important roles in plant tolerance to abiotic stress. [ABSTRACT FROM AUTHOR]

The experiment was conducted from 2011 to 2014 in the experimental fi eld of the Fruit growing department at the Agricultural University - Plovdiv, located near the village of Brestnik. The growth behaviour of the Florina cultivar grafted on the M9 rootstock was studied. The M9 rootstock had been produced in a stoolbed from plants with three different origins: from adventive buds at the roots; by clonal micropropagation technology and by somatic organogenesis from leaf explants. The highest thickening speed of the rootstocks in nursery, measured by the end of June, is observed in respect to the plants derived through somatic organogenesis. This also suggests earlier cambial activity. The vegetative growth of the cultivar slows down at the end of the first half of July. The highest total vegetative growth of the cultivar is achieved by the plant derived of the rootstock through somatic organogenesis from leaf explants. [ABSTRACT FROM AUTHOR]

Apple scab, caused by the apoplastic fungal pathogen Venturia inaequalis , is one of the most damaging apple diseases worldwide and scab resistance is still one of the most important goals in apple breeding programmes. Improving knowledge of defence systems against pathogens through the identification of resistance and defence-related genes enables the development of molecular tools that can be used for assisted-selection of elite varieties. The apple scab Rvi6 (formerly HcrVf2 ) resistance gene has been extensively used to breed resistant varieties, and several defence-related genes activated downstream have recently been identified. In this work, subtractive hybridisation was performed in order to collect cDNA differentially expressed in the resistant Rvi6 cultivar ‘Florina’ after challenge with the fungus and treatment with salicylic acid. A total of 97 unique sequences were identified, and most of them were successfully annotated and located on the apple genome in silico . The expression profiles of twelve candidate genes were analysed using quantitative real-time PCR in both incompatible and compatible Malus - V.inaequalis interactions. The responses induced by the two treatments differed significantly, suggesting that salicylic acid might be not involved in apple scab defence mechanisms. Some candidate genes are involved in well-known defence strategies against apoplastic fungal pathogens, such as the reinforcement and maintenance of cell wall integrity and fungal growth hindrance. Others are presumed to play a role in the signal transduction pathway, in a similar way to that known for other pathosystems. Finally, potential mechanisms involved in the defence response against apple scab are proposed. [ABSTRACT FROM AUTHOR]

Phloridzin (phloretin 2′- O -glucoside) is the most abundant phenolic compound in Malus species, accounting for up to 18% of the dry weight in leaves. Glycosylation of phloretin at the 2′ position is the last and key step in phloridzin biosynthesis. It is catalyzed by a uridine diphosphate (UDP)-glucose:phloretin 2′- O -glucosyltransferase (P2′GT), which directly determines the concentration of phloridzin. However, this process is poorly understood. We conducted a large-scale investigation of phloridzin accumulations in leaves from 64 Malus species and cultivars. To identify the responsible P2′GT, we performed a genome-wide analysis of the expression patterns of UDP-dependent glycosyltransferase genes ( UGT s). Two candidates were screened preliminarily in Malus spp. cv. Adams (North American Begonia). Results from further qRT-PCR analyses of the genotypes showed a divergence in phloridzin production. Our assays of enzyme activity also suggested that MdUGT88F4 and MdUGT88F1 regulate the conversion of phloretin to phloridzin in Malus plants. Finally, when they were silenced in ‘GL-3’ (‘Royal Gala’), the concentrations of phloridzin and phloretin (and trilobatin) were significantly reduced and increased, respectively. [ABSTRACT FROM AUTHOR]

MdMYB1 is an important regulator for anthocyanin accumulation in apple (Malus×domestica). Here, an apple RING E3 ligase, MdMIEL1, was screened out as a partner of MdMYB1 with a yeast two-hybrid approach. Pull-down, bimolecular fluorescence complementation and coimmunoprecipitation assays further verified the interaction between MdMIEL1 and MdMYB1 proteins. Subsequently, in vitro and in vivo experiments indicated that MdMIEL1 functioned as a ubiquitin E3 ligase to ubiquitinate MdMYB1 protein, followed by degradation through a 26S proteasome pathway. Furthermore, transgenic studies in apple calli and Arabidopsis demonstrated that MdMIEL1 negatively regulated anthocyanin accumulation by modulating the degradation of MdMYB1 protein. Taken together, our findings provide a new insight into the molecular mechanism by which MdMIEL1 negatively regulates anthocyanin biosynthesis by ubiquitinating and degrading MdMYB1 protein. [ABSTRACT FROM AUTHOR]

The nature and structure of genetic diversity in the Spanish apple germplasm preserved at the national level was widely unknown, since studies performed to date on this topic have been exclusively carried out at the regional scale. Here, 1453 accessions from Spanish collections of Malus × domestica were evaluated with a common set of 13 SSR (Simple Sequence Repeats) markers in order to estimate genetic diversity, to identify the underlying genetic structure and to unravel the relationships among them and among a wide set of international cultivars for reference. In total, 737 unique genotypes were identified, 581 diploids and 156 triploids. Using a model-based Bayesian clustering procedure, two reconstructed populations were obtained for diploid genotypes; one retaining only Spanish cultivars (42% of genotypes), and a second containing all foreign cultivars the latter exhibiting evidence supporting the existence of a secondary sub-structure. Similarly, analysis performed on the 156 triploid genotypes also revealed two reconstructed populations; one exclusively associated with local Spanish genotypes (44%). The Jaccard coefficient allowed clustering by UPGMA (Unweighted Pair Group Method) diploid and triploid genotypes, and remarkable differences in allelic composition among the different partitioning levels were found. AMOVA analyses showed moderate but significant differentiation among the main groups (0.08 ≤ F ST ≤ 0.12). Our results highlight an important fraction of the Spanish apple germplasm that constitutes a differentiated genepool with respect to the international and commercial apple cultivars. Moreover, the extent of the Spanish genetic diversity was spatially distributed along the northern Iberian Peninsula, suggesting an extensive migration of genotypes along the country. This study is the first valuable action for genetic conservation of apple at the national scale, and constitutes a decisive step towards the definition of a Spanish core collection that will be useful for further studies in dissecting the genetic control of important horticultural traits through genome-wide association analysis in apple. [ABSTRACT FROM AUTHOR]

Background: The plant-specific gibberellic acid stimulated Arabidopsis (GASA) gene family is critical for plant development. However, little is known about these genes, particularly in fruit tree species. Results: We identified 15 putative Arabidopsis thaliana GASA (AtGASA) and 26 apple GASA (MdGASA) genes. The identified genes were then characterized (e.g., chromosomal location, structure, and evolutionary relationships). All of the identified A. thaliana and apple GASA proteins included a conserved GASA domain and exhibited similar characteristics. Specifically, the MdGASA expression levels in various tissues and organs were analyzed based on an online gene expression profile and by qRT-PCR. These genes were more highly expressed in the leaves, buds, and fruits compared with the seeds, roots, and seedlings. MdGASA genes were also responsive to gibberellic acid (GA3) and abscisic acid treatments. Additionally, transcriptome sequencing results revealed seven potential flowering-related MdGASA genes. We analyzed the expression levels of these genes in response to flowering-related treatments (GA3, 6-benzylaminopurine, and sugar) and in apple varieties that differed in terms of flowering ('Nagafu No. 2' and 'Yanfu No. 6') during the flower induction period. These candidate MdGASA genes exhibited diverse expression patterns. The expression levels of six MdGASA genes were inhibited by GA3, while the expression of one gene was up-regulated. Additionally, there were expression-level differences induced by the 6-benzylaminopurine and sugar treatments during the flower induction stage, as well as in the different flowering varieties. Conclusion: This study represents the first comprehensive investigation of the A. thaliana and apple GASA gene families. Our data may provide useful clues for future studies and may support the hypotheses regarding the role of GASA proteins during the flower induction stage in fruit tree species. [ABSTRACT FROM AUTHOR]

Key message : Comparative ultrastructural developmental time-course analysis has identified discrete stages at which the fruit plastids undergo structural and consequently functional transitions to facilitate subsequent development-guided understanding of the complex plastid biology. Abstract: Plastids are the defining organelle for a plant cell and are critical for myriad metabolic functions. The role of leaf plastid, chloroplast, is extensively documented; however, fruit plastids-chromoplasts-are poorly understood, especially in the context of the diverse metabolic processes operating in these diverse plant organs. Recently, in a comparative study of the predicted plastid-targeted proteomes across seven plant species, we reported that each plant species is predicted to harbor a unique set of plastid-targeted proteins. However, the temporal and developmental context of these processes remains unknown. In this study, an ultrastructural analysis approach was used to characterize fruit plastids in the epidermal and collenchymal cell layers at 11 developmental timepoints in three genotypes of apple ( Malus × domestica Borkh.): chlorophyll-predominant 'Granny Smith', carotenoid-predominant 'Golden Delicious', and anthocyanin-predominant 'Top Red Delicious'. Plastids transitioned from a proplastid-like plastid to a chromoplast-like plastid in epidermis cells, while in the collenchyma cells, they transitioned from a chloroplast-like plastid to a chloro-chromo-amyloplast plastid. Plastids in the collenchyma cells of the three genotypes demonstrated a diverse array of structures and features. This study enabled the identification of discrete developmental stages during which specific functions are most likely being performed by the plastids as indicated by accumulation of plastoglobuli, starch granules, and other sub-organeller structures. Information regarding the metabolically active developmental stages is expected to facilitate biologically relevant omics studies to unravel the complex biochemistry of plastids in perennial non-model systems. [ABSTRACT FROM AUTHOR]