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Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental 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.)

To screen eminent litchi varieties suitable for the development of natural antioxidant products, the total phenol, total proanthocyanidin, total flavonoid contents and A-type oligomeric procyanidin fractions in the pericarps of seven diverse litchi cultivars were analyzed. The in vitro antioxidant activities including DPPH, ABTS+ free radical scavenging and FRAP were determined. The results demonstrated that the total phenols, total proanthocyanidins, total flavonoids as well as total A-type oligomeric procyanidins contained in the pericarp extract of 'Hemaoli' were the highest. In addition, the primary and secondary mass spectra of the contained substances were analyzed and identified by electrospray liquid-mass spectrometry with quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS/MS). The mass spectrometry results demonstrated that the oligomeric procyanidin fractions contained in litchi pericarps were mainly epicatechin, procyanidin A2, procyanidin A4, A-type trimer and tetramer. Moreover, the content of A-type oligomeric procyanidins in litchi pericarp varied significantly (P<0.05) among diverse cultivars. The pericarp extract of 'Hemaoli' possessed potent free radical scavenging activity (DPPH: 1144.60 μmol Trolox/g DW, ABTS+: 2905.56 μmol Trolox/g DW, FRAP: 868.84 μmol Trolox/g DW). The contents of A-type procyanidin monomer, dimer and trimer were significantly correlated with antioxidant activity by Pearson's correlation analysis (P<0.05). In summary, a comprehensive analysis indicated that the pericarp extract of 'Hemaoli' contained the highest content of A-type oligomeric procyanidins as well as remarkable antioxidant activity compared to other cultivars. Therefore, 'Hemaoli' could be utilized as a novel potential material for the development of natural antioxidant products. [ABSTRACT FROM AUTHOR]

Flower color variations have increasingly been recognized as playing an important role in the adaptation to UV-B radiation; however, the underlying mechanism is poorly understood in perennial fruit trees. Litchi is an important fruit tree, and extremely early maturing (EEM) and middle-to-late-maturing (MLM) cultivars that originated from regions with high and low UV-B radiation have dark brown and light yellow flower buds, respectively, while their hybrid early-maturing (EM) cultivars have an intermediate brown flower bud. This study comprehensively analyzed the metabolome and transcriptome of flower buds of litchi EEM, EM and MLM cultivars to explore the mechanism underlying flower color variation during the adaptation to UV-B radiation for the first time. Metabolomic analysis identified 72 flavonoids in litchi flower buds, among which a higher accumulation of flavonol glycosides was responsible for darker flower buds of EEM cultivars. And transcriptome analysis revealed key structural genes, including LcCHI, LcFLS and seven UGTs, together with two transcription factors (LcMYB12 and LcMYB111), which could be directly up-regulated by UV-B radiation, playing critical roles in regulating the differential accumulation of flavonol glycosides. These results provide new insights into the molecular mechanism underlying adaptation to UV-B radiation and provide a genetic basis for future breeding of stress-tolerant cultivars of litchi. [ABSTRACT FROM AUTHOR]

Real-time reverse transcription quantitative PCR (RT-qPCR) is an important tool for gene expression analysis. Suitable reference genes are the basis of accurate and reliable RT-qPCR results. Litchi (Litchi chinensis Sonn.) is a commercially important tropical and subtropical fruit, but rapid pericarp browning is a substantial negative impact on its commercial use. Reference gene validation could help in the screening for genes involved in the browning mechanism. We assessed 15 new candidate reference genes from litchi transcriptome to determine stable reference genes for RT-qPCR analysis of pericarps from different cultivars, with differing postharvest storage, and under pathogenic stress. Ct values, geNorm, Normfinder, and RefFinder algorithms, were used to identify genes with the most stable transcription. GAGA-25 was the gene with the most stable transcription for comparing different varieties of the fresh pericarp. HDAC9 was the gene with the most stable transcription for postharvest pericarp. STAM was the gene with the most stable transcription for inoculated pericarp. Of the candidate reference genes, GAGA-25 was the most stable reference gene across the complete sample set. This study evaluated reference gene stability for RT-qPCR in litchi pericarp. This work provides a foundation for using qPCR to study gene function and molecular mechanism studies of litchi pericarp browning. [ABSTRACT FROM AUTHOR]

Aroma is considered a fundamental component of fruit flavor. Variations in the composition and content of volatile organic compounds (VOCs) contribute to noticeable differences in fruit aromas. Litchi is a delicious tropical and subtropical fruit, and a large number of germplasm resources with unique aromas have emerged during the past 2000 years of cultivation. In this review, our aim is to collect, compare, integrate, and summarize the available literature on the profiles of VOCs of 25 litchi cultivars. We showed that a total of 556 VOCs were reported from litchi fruit, and the aroma of litchi is mainly determined from the content and composition of monoterpenoids and alcohols, including linalool, geraniol, limonene, terpinolene, β-citronellol, p-cymene, nerol, α-terpineol, cis-rose oxide, β-myrcene, 4-terpineol, citral, and neral (cis-citral), which might contribute to the rose-like or citrus-like aroma of litchi fruit. Moreover, sulfur-containing volatile compounds (VSCs) possibly impart a special flavor to litchi fruit. This review would be a valuable resource for researchers aiming to improve litchi aroma quality by elucidating the possible mechanisms underlying VOC biosynthesis and their metabolism in litchi fruit. [ABSTRACT FROM AUTHOR]

Real-time reverse transcription quantitative PCR (RT-qPCR) is an important tool for gene expression analysis. Suitable reference genes are the basis of accurate and reliable RT-qPCR results. Litchi (Litchi chinensis Sonn.) is a commercially important tropical and subtropical fruit, but rapid pericarp browning is a substantial negative impact on its commercial use. Reference gene validation could help in the screening for genes involved in the browning mechanism. We assessed 15 new candidate reference genes from litchi transcriptome to determine stable reference genes for RT-qPCR analysis of pericarps from different cultivars, with differing postharvest storage, and under pathogenic stress. Ct values, geNorm, Normfinder, and RefFinder algorithms, were used to identify genes with the most stable transcription. GAGA-25 was the gene with the most stable transcription for comparing different varieties of the fresh pericarp. HDAC9 was the gene with the most stable transcription for postharvest pericarp. STAM was the gene with the most stable transcription for inoculated pericarp. Of the candidate reference genes, GAGA-25 was the most stable reference gene across the complete sample set. This study evaluated reference gene stability for RT-qPCR in litchi pericarp. This work provides a foundation for using qPCR to study gene function and molecular mechanism studies of litchi pericarp browning. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of three different drying methods, freeze drying (FD), vacuum drying (VD) and oven drying (OD) on phenolic contents and antioxidant activities of litchi fruits. 20 polyphenols were exactly identified in the litchi fruits by UPLC-QqQ/MS. Significant losses were observed in the contents of total polyphenols and antioxidant activities in the dried litchi when compared with the fresh litchi. Principle component analysis indicated that there was significant difference of phenolic component between the use of thermal drying (VD and OD) and FD. Our results suggest that FD is the optimum drying method for litchi fruits considering the content of total polyphenols and antioxidant activities. [ABSTRACT FROM AUTHOR]

The residual sulfite caused by sulfur fumigation (SF) is a hazard to health and influenced the export trade of litchi. Desulfurization (DS) is a valid chemical method to reduce the residual sulfite. However, the effect of DS on fumigated litchi has not been studied at physiological and molecular level. This study was aimed to evaluate the effect of DS (SF plus 3% desulfurizer) on the postharvest quality, sulfite residue, and the sulfite metabolism in sulfitated "Feizixiao" litchi during the 4°C storage. Results indicated that the DS promoted the color recovery of sulfitated litchi and achieved an effect similar to SF on controlling rot and browning. DS recovered the water content and respiration rate of sulfitated litchi pericarp. Thus, DS improves commodity properties of sulfitated litchi. Moreover, DS greatly reduced sulfite residue especially in pulp and ensured the edible safety of sulfitated litchi. The activities of sulfite oxidase, sulfite reductase, serine acetyltransferase, and O‐acetylserine(thiol) lyase in pulp increased after SF but fell down after DS while the expressions of their encoding genes decreased after SF but then rallied after DS. These results indicated the key role of these enzymes in sulfite metabolism after SF and DS changed the sulfite metabolism at both enzymatic and transcriptional level. It could be concluded that DS used in this study was an effective method for improving the color recovery and ensuring the edible safety of sulfitated litchi by not only chemical reaction but also both of enzymatic and transcriptional regulation. [ABSTRACT FROM AUTHOR]

Litchi (Litchi chinensis) is an important subtropical fruit tree with high commercial value. However, the short and centralized fruit maturation period of litchi cultivars represents a bottleneck for litchi production. Therefore, the development of novel cultivars with extremely early fruit maturation period is critical. Previously, we showed that the genotypes of extremely early-maturing (EEM), early-maturing (EM), and middle-to-late-maturing (MLM) cultivars at a specific locus SNP51 (substitution type C/T) were consistent with their respective genetic background at the whole-genome level; a homozygous C/C genotype at SNP51 systematically differentiated EEM cultivars from others. The litchi gene on which SNP51 was located was annotated as flavonol synthase (FLS), which catalyzes the formation of flavonols. Here, we further elucidate the variation of the FLS gene from L. chinensis (LcFLS) among EEM, EM, and MLM cultivars. EEM cultivars with a homozygous C/C genotype at SNP51 all contained the same 2,199-bp sequence of the LcFLS gene. For MLM cultivars with a homozygous T/T genotype at SNP51, the sequence lengths of the LcFLS gene were 2,202-2,222 bp. EM cultivars with heterozygous C/T genotypes at SNP51 contained two different alleles of the LcFLS gene: a 2,199-bp sequence identical to that in EEM cultivars and a 2,205-bp sequence identical to that in MLM cultivar 'Heiye.' Moreover, the coding regions of LcFLS genes of other MLM cultivars were almost identical to that of 'Heiye.' Therefore, the LcFLS gene coding region may be used as a source of diagnostic SNP markers to discriminate or identify genotypes with the EEM trait. The expression pattern of the LcFLS gene and accumulation pattern of flavonol from EEM, EM, and MLM cultivars were analyzed and compared using quantitative real-time PCR (qRT-PCR) and high-performance liquid chromatography (HPLC) for mature leaves, flower buds, and fruits, 15, 30, 45, and 60 days after anthesis. Flavonol content and LcFLS gene expression levels were positively correlated in all three cultivars: both decreased from the EEM to MLM cultivars, with moderate levels in the EM cultivars. LcFLS gene function could be further analyzed to elucidate its correlation with phenotype variation among litchi cultivars with different fruit maturation periods. [ABSTRACT FROM AUTHOR]

Abstract Oxidation of anthocyanin by polyphenol oxidase (PPO) or peroxidase (POD) causes enzymatic browning. It leads to undesirable characteristics of fruits and ultimately decreasing of fruit quality and value. Desiccation, post-harvest decay, loss of quality and micro cracking are the other most important problems restricting the growth of the litchi industry. Based on the fact, glutathione and citric acid inhibits the browning mechanism, the novel strategies of combining glutathione + citric acid with different packaging materials were used to improve litchi storability at refrigerated and room temperature. From the experiment, it was observed that, the application of glutathione (10 mmol/litre) and citric acid (100 mmol/litre) + polypropylene packet + corrugated fiber box gave good control on browning, weight loss, disease incidence and higher amount of anthocyanin in the litchi pericarp. High amount of TSS, total sugar, titratable acidity and ascorbic acid were also achieved in same treatments. Litchi fruits treated with combined application of glutathione and citric acid with packaging materials showed promising method to controlling browning and all the other quality parameters. [ABSTRACT FROM AUTHOR]

The extraction of litchi ( Litchi chinensis Sonn.) and oat ( Avena sativa L.) seeds were investigated using n-butane as pressurized solvent by evaluating the effect of pressure in the range of 7-100 bar and temperature from 25 to 70 °C on the extract yield and chemical composition together with the antioxidant activity of the extracts obtained. It was experimentally observed extraction yields for both seeds up to ~3.5 wt%, with a total phenolic content around 126.4 mg GAE/100 g of extract, and an antioxidant activity up to 78.36%. Oat seeds extract presented higher values of these parameters evaluated compared to litchi extract. Based on the results found, it seems that n-butane may be a promising solvent to conventional extraction methods, as mild operating conditions and eco-friendly solvent can be used to provide good results without any residues in the final product. [ABSTRACT FROM AUTHOR]

Tropical evergreen perennials undergo recurrent flush growth, and their terminal buds alternate between growth and dormancy. In sharp contrast to the intensive studies on bud development in temperate deciduous trees, there is little information about bud development regulation in tropical trees. In this study, litchi (Litchi chinensis Sonn.) was used as a model tropical perennial for morphological characterization and transcriptomic analysis of bud development. Litchi buds are naked with apical meristem embraced by rudimentary leaves, which are brown at dormant stage (Stage I). They swell and turn greenish as buds break (Stage II), and as growth accelerates, the rudimentary leaves elongate and open exposing the inner leaf primodia. With the outgrowth of the needle-like leaflets, bud growth reaches a maximum (Stage III). When leaflets expand, bud growth cease with the abortion of the rudimentary leaves at upper positions (Stage IV). Then buds turn brown and reenter dormant status. Budbreak occurs again when new leaves become hard green. Buds at four stages (Stage I to IV) were collected for respiration measurements and in-depth RNA sequencing. Respiration rate was the lowest at Stage I and highest at Stage II, decreasing toward growth cessation. RNA sequencing obtained over 5 Gb data from each of the bud samples and de novo assembly generated a total of 59,999 unigenes, 40,119 of which were annotated. Pair-wise comparison of gene expression between stages, gene profiling across stages, GO/KEGG enrichment analysis, and the expression patterns of 17 major genes highlighted by principal component (PC) analysis displayed significant changes in stress resistance, hormone signal pathways, circadian rhythm, photosynthesis, cell division, carbohydrate metabolism, programmed cell death during bud development, which might be under epigenetic control involving chromatin methylation. The qPCR results of 8 selected unigenes with high PC scores agreed with the RPKM values obtained from RNA-seq. Three Short Vegetative Phase (SVP) genes, namely LcSVP1, LcSVP2, and LcSVP3 displayed different expression patterns, suggesting their differential roles in bud development regulation. The study brought an understanding about biological processes associated with the phase transitions, molecular regulation of bud development, as well as cyclic bud growth as a strategy to survive tropical conditions. [ABSTRACT FROM AUTHOR]

Glycosylation plays a major role in the diversity in the chemical compositions of flavonoids. In this study, we performed biochemical and molecular assays to identify a glucosyltransferase gene responsible for the anthocyanin composition in litchi. Cyanidin-3-glucoside and cyanidin-3-rutinoside were predominant anthocyanins in the red pericarp and young leaf of litchi. Anthocyanin composition varied among litchi varieties. Anthocyanin profile was primarily determined by genetic factors. Higher activities of UDP-rhamnose: cyanidin-3-glucoside rhamnosyltransferase (CGRT) were detected in the pericarps of the cyanidin-3-rutinoside predominant varieties. Three full-length putative UDP-rhamnose: flavonoid glycoside 2″-O-beta-l-rhamnosyltransferase-like genes were isolated and designated as LcFGRT2, LcFGRT4, and LcFGRT5. Phylogenetic analysis showed that these genes were clustered with other glucoside-glycosyltransferases. Notable activities in catalyzing cyanidin-3-rutinoside formation were observed in extracts of tobacco leaves and yeast with heterologous expression of LcFGRT4. However, the expression pattern of LcFGRT4 did not agree with the CGRT activity. This result suggests that the difference in CGRT among varieties occurred post-transcriptionally. Nucleotide variation in LcFGRT4 was surveyed by sequencing 30 litchi accessions with different anthocyanin profiles. Eight non-synonymous single-nucleotide polymorphisms were detected. Type A LcFGRT4 sequence (LcFGRT4A) was observed in cyanidin-3-glucoside-dominant varieties, whereas type B LcFGRT4 sequence (LcFGRT4B) was detected in cyanidin-3-glucoside-dominant varieties. A mutant in 343 C/G polymorphism was targeted as the critical point responsible for the CGRT activity. Results indicated that a single-point mutation in LcFGRT4 could alter the activity of CGRT and may contribute to the diverse anthocyanin profile of litchi. [ABSTRACT FROM AUTHOR]

Key message: A novel LcGST4 was identified and characterized from Litchi chinensis . Expression and functional analysis demonstrated that it might function in anthocyanin accumulation in litchi. Abstract: Glutathione S-transferases (GSTs) have been defined as detoxification enzymes for their ability to recognize reactive electrophilic xenobiotic molecules as well as endogenous secondary metabolites. Anthocyanins are among the few endogenous substrates of GSTs for vacuolar accumulation. The gene encoding a GST protein that is involved in anthocyanin sequestration from Litchi chinensis Sonn. has not been reported. Here, LcGST4, an anthocyanin-related GST, was identified and characterized. Phylogenetic analysis showed that LcGST4 was clustered with other known anthocyanin-related GSTs in the same clade. Expression analysis revealed that the expression pattern of LcGST4 was strongly correlated with anthocyanin accumulation in litchi. ABA- and light-responsive elements were found in the LcGST4 promoter, which is in agreement with the result that the expression of LcGST4 was induced by both ABA and debagging treatment. A GST activity assay in vitro verified that the LcGST4 protein shared universal activity with the GST family. Functional complementation of an Arabidopsis mutant tt19 demonstrated that LcGST4 might function in anthocyanin accumulation in litchi. Dual luciferase assay revealed that the expression of LcGST4 was activated by LcMYB1, a key R2R3-MYB transcription factor that regulates anthocyanin biosynthesis in litchi. [ABSTRACT FROM AUTHOR]

The high level of physiological fruitlet abscission in litchi (Litchi chinensis Sonn.) causes severe yield loss. Cell separation occurs at the fruit abscission zone (FAZ) and can be triggered by ethylene. However, a deep knowledge of the molecular events occurring in the FAZ is still unknown. Here, genome-wide digital transcript abundance (DTA) analysis of putative fruit abscission related genes regulated by ethephon in litchi were studied. More than 81 million high quality reads from seven ethephon treated and untreated control libraries were obtained by high-throughput sequencing. Through DTA profile analysis in combination with Gene Ontology and KEGG pathway enrichment analyses, a total of 2730 statistically significant candidate genes were involved in the ethephon-promoted litchi fruitlet abscission. Of these, there were 1867 early-responsive genes whose expressions were up- or down-regulated from 0 to 1 d after treatment. The most affected genes included those related to ethylene biosynthesis and signaling, auxin transport and signaling, transcription factors (TFs), protein ubiquitination, ROS response, calcium signal transduction, and cell wall modification. These genes could be clustered into four groups and 13 subgroups according to their similar expression patterns. qRT-PCR displayed the expression pattern of 41 selected candidate genes, which proved the accuracy of our DTA data. Ethephon treatment significantly increased fruit abscission and ethylene production of fruitlet. The possible molecular events to control the ethephon-promoted litchi fruitlet abscission were prompted out. The increased ethylene evolution in fruitlet would suppress the synthesis and polar transport of auxin and trigger abscission signaling. To the best of our knowledge, it is the first time to monitor the gene expression profile occurring in the FAZ-enriched pedicel during litchi fruit abscission induced by ethephon on the genome-wide level. This study will contribute to a better understanding for the molecular regulatory mechanism of fruit abscission in litchi. [ABSTRACT FROM AUTHOR]

Massive young fruit abscission usually causes low and unstable yield in litchi (Litchi chinensis Sonn.), an important fruit crop cultivated in tropical and subtropical areas. However, the molecular mechanism of fruit drop has not been fully characterized. This study aimed at identification of molecular components involved in fruitlet abscission in litchi, for which reference genome is not available at present. An improved de novo transcriptome assembly was firstly achieved by using an optimized assembly software, Trinity. Using improved transcriptome assembly as reference, digital transcript abundance (DTA) profiling was performed to screen and identify candidate genes involved in fruit abscission induced by girdling plus defoliation (GPD), a treatment significantly decreased the soluble sugar contents causing carbohydrate stress to fruit. Our results showed that the increasing fruit abscission rate after GPD treatment was associated with higher ethylene production and lower glucose levels in fruit. A total of 2,771 differentially expressed genes were identified as GPD-responsive genes, 857 of which were defined by GO and KEGG enrichment analyses as the candidate genes involved in fruit abscission process. These genes were involved in diverse metabolic processes and pathways, including carbohydrate metabolism, plant hormone synthesis, and signaling, transcription factor activity and cell wall modification that were rapidly induced in the early stages (within 2 days after treatment). qRT-PCR was used to explore the expression pattern of 15 selected candidate genes in the abscission zone, pericarp, and seed, which confirmed the accuracy of our DTA data. More detailed information for different functional categories was also analyzed. This study profiled the gene expression related to fruit abscission induced by carbohydrate stress at whole transcriptome level and thus provided a better understanding of the regulatory mechanism of young fruit abscission in litchi. [ABSTRACT FROM AUTHOR]

The high level of physiological fruitlet abscission in litchi (Litchi chinensis Sonn.) causes severe yield loss. Cell separation occurs at the fruit abscission zone (FAZ) and can be triggered by ethylene. However, a deep knowledge of the molecular events occurring in the FAZ is still unknown. Here, genome-wide digital transcript abundance (DTA) analysis of putative fruit abscission related genes regulated by ethephon in litchi were studied. More than 81 million high quality reads from seven ethephon treated and untreated control libraries were obtained by high-throughput sequencing. Through DTA profile analysis in combination with Gene Ontology and KEGG pathway enrichment analyses, a total of 2730 statistically significant candidate genes were involved in the ethephon-promoted litchi fruitlet abscission. Of these, there were 1867 early-responsive genes whose expressions were up- or down-regulated from 0 to 1 d after treatment. The most affected genes included those related to ethylene biosynthesis and signaling, auxin transport and signaling, transcription factors (TFs), protein ubiquitination, ROS response, calcium signal transduction, and cell wall modification. These genes could be clustered into four groups and 13 subgroups according to their similar expression patterns. qRT-PCR displayed the expression pattern of 41 selected candidate genes, which proved the accuracy of our DTA data. Ethephon treatment significantly increased fruit abscission and ethylene production of fruitlet. The possible molecular events to control the ethephon-promoted litchi fruitlet abscission were prompted out. The increased ethylene evolution in fruitlet would suppress the synthesis and polar transport of auxin and trigger abscission signaling. To the best of our knowledge, it is the first time to monitor the gene expression profile occurring in the FAZ-enriched pedicel during litchi fruit abscission induced by ethephon on the genome-wide level. This study will contribute to a better understanding for the molecular regulatory mechanism of fruit abscission in litchi. [ABSTRACT FROM AUTHOR]

Litchi ( Litchi chinensis Sonn., L. chinensis), a type of tree growing in most areas of southern China, produces an edible fruit that is also a source of traditional medicine. Genetic identification of litchi species or cultivars using molecular markers is very important. In this study, a total of six litchi samples from Fujian, Hainan, Guangdong, Guangxi and Sichuan province, as well as one wild Dimocarpus confinis ( D. confinis) sample from Guangxi province were collected for genetic analysis. The cluster dendrograms were constructed for genetic analysis on the basis of DNA amplification results by RAPD and ISSR. The improved RAPD amplified DNA with consistent and clear banding patterns. A total of 176 bands were found, indicating a 72.7 % polymorphism in L. chinensis DNA samples. Significant genetic distances were found among the different species or cultivars, with an index of similarity coefficient ranging from 0.59 to 0.87. Similar to RAPD results, ISSR analysis of the L. chinensis DNA samples showed a range of 0.70-0.93 similarity coefficients. The genetic distance between Hainan sample and Sichuan samples was the farthest, which is consistent with their geographic distance. Furthermore, the index of similarity coefficient between D. confinis and L. chinensis was 0.35-0.41 by RAPD and 0.38-0.48 by ISSR, indicating that these two species have significant genetic difference. This study reveals the high level of genetic differences between different litchi species or cultivars, and confirms the significance of the improved RAPD method in genetic characterization of organisms. Taken together, the improved RAPD combined with ISSR analysis can be used frequently for the genetic diversity, germplasm resources preservation, molecular-assisted breeding, and genetic characterization of various organisms. [ABSTRACT FROM AUTHOR]

Auxin, a vital plant hormone, regulates a variety of physiological and developmental processes. It is involved in fruit abscission through transcriptional regulation of many auxin-related genes, including early auxin responsive genes (i.e., auxin/indole-3-acetic acid (AUX/IAA), Gretchen Hagen3 (GH3) and small auxin upregulated (SAUR)) and auxin response factors (ARF), which have been well characterized in many plants. In this study, totally five auxin-related genes, including one AUX/IAA (LcAUX/IAA1), one GH3 (LcGH3.1), one SAUR (LcSAUR1) and two ARFs (LcARF1 and LcARF2), were isolated and characterized from litchi fruit. LcAUX/IAA1, LcGH3.1, LcSAUR1, LcARF1 and LcARF2 contain open reading frames (ORFs) encoding polypeptides of 203, 613, 142, 792 and 832 amino acids, respectively, with their corresponding molecular weights of 22.67, 69.20, 11.40, 88.20 and 93.16 kDa. Expression of these genes was investigated under the treatment of girdling plus defoliation which aggravated litchi fruitlet abscission due to the blockage of carbohydrates transport and the reduction of endogenous IAA content. Results showed that transcript levels of LcAUX/IAA1, LcGH3.1 and LcSAUR1 mRNAs were increased after the treatment in abscission zone (AZ) and other tissues, in contrast to the decreasing accumulation of LcARF1 mRNA, suggesting that LcAUX/IAA1, LcSAUR1 and LcARF1 may play more important roles in abscission. Our results provide new insight into the process of fruitlet abscission induced by carbohydrate stress and broaden our understanding of the auxin signal transduction pathway in this process at the molecular level. [ABSTRACT FROM AUTHOR]

Copyright of Revista Ceres is the property of Revista Ceres 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.)

Lychee ( Litchi chinensis Sonn.) flower is a major nectar source in Taiwan. Antioxidant activities of acetone, ethanol, and hot-water extracts of the flower were estimated through three biochemical models: inhibition of Cu-induced oxidation of human low-density lipoprotein, scavenging ability of oxygen radicals in human blood, and inhibition of human erythrocyte hemolysis induced by peroxyl radicals. Composition and content of flavonoids and phenolic acids in these extracts were also determined by high-performance liquid chromatography. Results showed that antioxidant effects of all test models as well as contents of flavonoids and phenolic acids for the lychee flower extracts were in the order: acetone extract > ethanol extract > hot-water extract. Gentistic acid and epicatechin were the major phenolic acid and flavonoid in the extracts, respectively. [ABSTRACT FROM AUTHOR]

Litchi (Litchi chinensis Sonn.) 'Mauritius' is a popular export cultivar due to its attractive red color and excellent fruit quality. Three orchards were selected based on planting distance and routine pruning practices followed by each growing season. Orchards A and B are essentially similar regarding these production practices, whereas orchard C had overlapping canopies due to lack of routine pruning practices after each growing season and short planting distance. Canonical variate analysis was used as a statistical tool to compare fruit quality attributes from different orchards (A, B, and C) in terms of physical, chemical and sensory parameters and correlating to leaf nutrient status. The correlations and plot of loadings of the variates indicated that skin color (visual), color values (chroma and hue angle, h°), fruit weight, firmness, and consumer acceptability were the main factors that discriminated orchard C from the other two orchards. The soluble solids concentrations, titratable acidity and fruit taste were the quality attributes discriminating orchard A from orchard B. The relationship between the leaf nutrients and fruit quality attributes showed positive relationships between leaf potassium (K) and anthocyanin content and titratable acidity (TA); leaf phosphorus (P) and pericarp h°, leaf nitrogen (N) and fruit weight; leaf calcium (Ca) and fruit firmness. [ABSTRACT FROM AUTHOR]

Fruit cracking is a disorder of fruit development in response to internal or external cues, which causes a loss in the economic value of fruit. Therefore, exploring the mechanism underlying fruit cracking is of great significance to increase the economic yield of fruit trees. However, the molecular mechanism underlying fruit cracking is still poorly understood. Litchi, as an important tropical and subtropical fruit crop, contributes significantly to the gross agricultural product in Southeast Asia. One important agricultural concern in the litchi industry is that some famous varieties with high economic value such as 'Nuomici' are susceptible to fruit cracking. Here, the cracking-susceptible cultivar 'Nuomici' and cracking-resistant cultivar 'Huaizhi' were selected, and the samples including pericarp and aril during fruit development and cracking were collected for RNA-Seq analysis. Based on weighted gene co-expression network analysis (WGCNA) and the "ball-skin versus bladder effect" theory (fruit cracking occurs upon the aril expanding pressure exceeds the pericarp strength), it was found that seven co-expression modules genes (1733 candidate genes) were closely associated with fruit cracking in 'Nuomici'. Importantly, we propose that the low expression level of genes related to plant hormones (Auxin, Gibberellins, Ethylene), transcription factors, calcium transport and signaling, and lipid synthesis might decrease the mechanical strength of pericarp in 'Nuomici', while high expression level of genes associated with plant hormones (Auxin and abscisic acid), transcription factors, starch/sucrose metabolism, and sugar/water transport might increase the aril expanding pressure, thereby resulting in fruit cracking in 'Nuomici'. In conclusion, our results provide comprehensive molecular events involved in the "ball-skin versus bladder effect" on fruit cracking in litchi. [ABSTRACT FROM AUTHOR]