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Fruit size is an important fruit quality trait that influences the production and commodity values of loquats ( Eriobotrya japonica Lindl.). The Small Auxin Upregulated RNA ( SAUR ) gene family has proven to play a vital role in the fruit development of many plant species. However, it has not been comprehensively studied in a genome-wide manner in loquats, and its role in regulating fruit size remains unknown. In this study, we identified 95 EjSAUR genes in the loquat genome. Tandem duplication and segmental duplication contributed to the expansion of this gene family in loquats. Phylogenetic analysis grouped the SAURs from Arabidopsis , rice, and loquat into nine clusters. By analyzing the transcriptome profiles in different tissues and at different fruit developmental stages and comparing two sister lines with contrasting fruit sizes, as well as by functional predictions, a candidate gene ( EjSAUR22 ) highly expressed in expanding fruits was selected for further functional investigation. A combination of Indoleacetic acid (IAA) treatment and virus-induced gene silencing revealed that EjSAUR22 was not only responsive to auxin, but also played a role in regulating cell size and fruit expansion. The findings from our study provide a solid foundation for understanding the molecular mechanisms controlling fruit size in loquats, and also provide potential targets for manipulation of fruit size to accelerate loquat breeding.

Whole-genome duplication (WGD) plays important roles in plant evolution and function, yet little is known about how WGD underlies metabolic diversification of natural products that bear significant medicinal properties, especially in nonmodel trees. Here, we reveal how WGD laid the foundation for co-option and differentiation of medicinally important ursane triterpene pathway duplicates, generating distinct chemotypes between species and between developmental stages in the apple tribe. After generating chromosome-level assemblies of a widely cultivated loquat variety and Gillenia trifoliata, we define differentially evolved, duplicated gene pathways and date the WGD in the apple tribe at 13.5 to 27.1 Mya, much more recent than previously thought. We then functionally characterize contrasting metabolic pathways responsible for major triterpene biosynthesis in G. trifoliata and loquat, which pre- and postdate the Maleae WGD, respectively. Our work mechanistically details the metabolic diversity that arose post-WGD and provides insights into the genomic basis of medicinal properties of loquat, which has been used in both traditional and modern medicines., Competing Interests: The authors declare no competing interest., (Copyright © 2021 the Author(s). Published by PNAS.)

Loquat (Eriobotrya japonica Lindl.) is divided into yellow- and white-fleshed based on the difference in fruit color, and the variations in carotenoids accumulation are considered as the main reasons for this difference. Using RNA-seq technology, a transcriptome analysis was carried out on the flesh and peel of 'Baiyu' fruit during four different fruit development stages. A total of 172.53 Gb clean reads with an average of 6.33 Gb reads were detected for each library, and the percentage of Q30 was higher than 90.84%. We identified 16 carotenogenic and 13 plastid-lipid-associated protein (PAP) genes through RNA-seq. Of these, five carotenogenic and four PAP related genes exhibited remarkable differences in the expression patterns. Carotenoids biosynthetic genes, including DXS, PSY1 and VDE displayed higher expression levels in peel than that in the flesh. However, carotenoids decomposition gene, such as NCDE1, exhibited higher expression in flesh than that in the peel. Notably, all differentially expressed PAP genes showed higher expression levels in peel than flesh. We inferred that the differential accumulation of carotenoids in flesh and peel of 'Baiyu' is caused by the up- or down-regulation of the carotenogenic and PAP related genes. The functional analysis of these important genes will provide valuable information about underlying molecular mechanism of carotenoids accumulation in loquat., Competing Interests: The authors have declared that no competing interests exist.

The age pathway is important for regulating flower bud initiation in flowering plants. The major regulators in this pathway are miR156 and SPL transcription factors. To date, SPL genes have been identified in many species of plants. Loquat, as a woody fruit tree of Rosaceae, is unique in flowering time as it blooms in winter. However, the study of its SPL homologous genes on the regulation mechanism of flowering time is still limited. In this study, four SPL homologs- EjSPL3 , EjSPL4 , EjSPL5, and EjSPL9 -are cloned from loquat, and phylogenetic analysis showed that they share a high sequence similarity with the homologues from other plants, including a highly conserved SQUAMOSA promoter binding protein (SBP)-box domain. EjSPL3, EjSPL4, EjSPL5 are localized in the cytoplasm and nucleus, and EjSPL9 is localized only in the nucleus. EjSPL4, EjSPL5, and EjSPL9 can significantly activate the promoters of EjSOC1-1 , EjLFY-1, and EjAP1-1 ; overexpression of EjSPL3 , EjSPL4 , EjSPL5, and EjSPL9 in wild-type Arabidopsis thaliana can promote flowering obviously, and downstream flowering genes expression were upregulated. Our work indicated that the EjSPL3, EjSPL4, EjSPL5, and EjSPL9 transcription factors are speculated to likely participate in flower bud differentiation and other developmental processes in loquat. These findings are helpful to analyze the flowering regulation mechanism of loquat and provide reference for the study of the flowering mechanism of other woody fruit trees.

Flowering plants have evolved different flowering habits to sustain long-term reproduction. Most woody trees experience dormancy and then bloom in the warm spring, but loquat blooms in the cold autumn and winter. To explore its mechanism of flowering regulation, we cloned two SHORT VEGETATIVE PHASE (SVP) homologous genes from 'Jiefanzhong' loquat ( Eriobotrya japonica Lindl.), namely, EjSVP1 and EjSVP2 . Sequence analysis revealed that the EjSVPs were typical MADS-box transcription factors and exhibited a close genetic relationship with other plant SVP/DORMANCY-ASSOCIATED MADS-BOX (DAM) proteins. The temporal and spatial expression patterns showed that EjSVP1 and EjSVP2 were mainly expressed in the shoot apical meristem (SAM) after the initiation of flowering; after reaching their highest level, they gradually decreased with the development of the flower until they could not be detected. EjSVP1 expression levels were relatively high in young tissues, and EjSVP2 expression levels were relatively high in young to mature transformed tissues. Interestingly, EjSVP2 showed relatively high expression levels in various flower tissues. We analyzed the EjSVP promoter regions and found that they did not contain the C-repeat/dehydration-responsive element. Finally, we overexpressed the EjSVPs in wild-type Arabidopsis thaliana Col-0 and found no significant changes in the number of rosette leaves of Arabidopsis thaliana ; however, overexpression of EjSVP2 affected the formation of Arabidopsis thaliana flower organs. In conclusion, EjSVPs were found to play an active role in the development of loquat flowering. These findings may provide a reference for exploring the regulation mechanisms of loquat flowering and the dormancy mechanisms of other plants.

A novel peptidomics approach was used to discover cold-induced peptides in loquat fruit. Twenty unique peptides derived from 18 proproteins were identified, and they were involved in sugar signalling, protein metabolism and stress response. The quantitative analysis revealed 7 peptides with more than 2-fold upregulation, especially a 4.96-fold increase detected in the phytosulfokine (PSK) peptide. To further evaluate effects of PSK1 on fruit chilling tolerance, weight loss, firmness and internal browning were investigated in PSK1-treated loquat fruit at 0°C. By contrast, these chilling injury symptoms were effectively reduced by PSK1. PSK1 markedly delayed decreases of ATP content and energy charge. The PSK1-treated fruit exhibited significantly lower activities of cell-wall degrading enzymes and transcripts of genes related to lignin synthesis. Our results demonstrated that PSK1 improves chilling tolerance of loquat fruit by maintaining high energy status and cell integrity. Peptidomics analysis provides a promising tool to discover some key peptides., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Abstract: Restriction site‐associated DNA sequencing (RAD‐seq) was used to illuminate the genetic relationships among Eriobotrya species. The raw data were filtered, and 221 million clean reads were used for further analysis. A total of 1,983,332 SNPs were obtained from 23 Eriobotrya species and two relative genera. We obtained similar results by neighbor‐joining and maximum likelihood phylogenetic trees. All Eriobotrya plants grouped together into a big clade, and two out‐groups clustered together into a single or separate clade. Chinese and Vietnam accessions were distributed throughout the dendrogram. There was nonsignificant correlation between genotype and geographical distance. However, clustering results were correlated with leaf size to some extent. The Eriobotrya species could be divided into following three groups based on leaf size and phylogenetic analysis: group A and group B comprised of small leaves with <10 cm length except E. stipularis (16.76 cm), and group C can be further divided into two subgroups, which contained medium‐size leaves with a leaf length ranged from 10 to 20 cm and a leaf length bigger than 20 cm. [ABSTRACT FROM AUTHOR]

Abstract: Although most of the species in Eriobotrya originated in China there are few studies on the genetics and genetic relationship of this genus. The aim of the present study was to clarify genetic relationships among 18 Eriobotrya accessions from China using amplified fragment length polymorphism (AFLP). Two close relatives Raphiolepis indica (L.) Lindl. and Photinia serrulata Lindl. were used as outgroups. The results showed that 5 selected AFLP primer combinations amplified 297 scorable bands, of which 282 were polymorphic, yielding a polymorphism rate of 95%. Genetic similarity coefficient among Eriobotrya accessions ranged from 0.82 (between E. bengalensis Hook.f. and E. bengalensis forma angustifolia Vidal) to 0.41 (between E. serrate Vidal and E. deflexa Nakai) indicating substantial genetic variations in the Eriobotrya accessions evaluated. The unweighted pair-group method of arithmetic averages (UPGMA) cluster analysis, based on genetic similarity coefficient, produced a dendrogram which grouped 20 accessions into three main clusters. The result of cluster analysis was generally in agreement with the known taxonomic grouping. Furthermore, the clustering of the 18 accessions of Eriobotrya was consistent with systematic classification based on morphological characteristics. [Copyright &y& Elsevier]

Develop from flower tube, loquat ( Eriobotrya japonica Lindl.) fruit differs from apple and other pome on size and shape greatly. To date, cell regulators of loquat fruit morphogenesis are still unknown. Fruit growth, histological observation and regulatory genes expression were investigated for 22 stages in loquat. Growth measurements reveal that loquat contains larger carpel volume and thinner flesh compared to apple. Cellular analyses demonstrate that cell number contributes to size varieties among loquat and other pome. Low cell production rate confers to weak cell proliferation capacity during early development. The correlation of cell number/size changes and several regulatory gene expression implies that: loquat fruit maintained cell division under regulation of EjFWL s and other genes from anthesis to 42 days past anthesis; unique temporal expression of EjWEE1 and EjKRP3 at 42 and 63 days past anthesis participate in cell cycle exit and polyploidy establishment; complementary expression of EjCCS52 isoforms promotes cell growth in an endoreduplication dependent pathway like EjWEE1 and EjKRP3 may be involved; EjEXPA s involved in acid cell growth play crucial role in fruit cell size enlargement. Together, these data indicate that cell division and expansion under complicated regulation, and weak cell proliferation capacity result to less cell layer which confers to thin cortex. [ABSTRACT FROM AUTHOR]