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Pectins are synthesized and secreted to the cell wall as highly methyl-esterified polymers and demethyl-esterified by pectin methylesterases (PMEs), which are regulated by pectin methylesterase inhibitors (PMEIs). PMEs and PMEIs are involved in pectin degradation during fruit softening; however, the roles of the PME and PMEI gene families during fruit softening remain unclear. Here, 71 PME and 30 PMEI genes were identified in the peach (Prunus persica) genome and shown to be unevenly distributed on all eight chromosomes. The 71 PME genes comprised 36 Type-1 PMEs and 35 Type-2 PMEs. Transcriptome analysis showed that 11 PME and 15 PMEI genes were expressed during fruit ripening in melting flesh (MF) and stony-hard (SH) peaches. Three PME and five PMEI genes were expressed at higher levels in MF than in SH fruit and exhibited softening-associated expression patterns. Upstream regulatory cis elements of these genes related to hormone response, especially naphthaleneacetic acid and ethylene, were investigated. One PME (Prupe.7G192800) and two PMEIs (Prupe.1G114500 and Prupe.2G279800), and their promoters were identified as potential targets for future studies on the biochemical metabolism and regulation of fruit ripening. The comprehensive data generated in this study will improve our understanding of the PME and PMEI gene families in peach. However, further detailed investigation is necessary to elucidate the biochemical function and regulation mechanism of the PME and PMEI genes during peach fruit ripening.
Cultivated peach (Prunus persica) is an important fruit species worldwide. The wild relatives in Prunus, such as P. mira, P. davidiana, P. kansuensis, P. ferganensis, and P. persica, are valuable for peach breeding, and early and accurate identification of parental and hybrid genotypes is critical. In this study, 20 representative accessions of peach germplasm from the National Germplasm Repository of Peach in China were used to select a set of 18 simple sequence repeat (SSR) markers for accurate species discrimination. Eight unknown peach samples were successfully identified using the SSR panel and species genotype database. Interspecific hybrid genotypes of P. persica × P. davidiana, P. persica × P. kansuensis, and P. persica × P. ferganensis were also analyzed reliably. The markers were amenable to high-throughput fluorescent labeling and capillary electrophoresis (CE) analysis, allowing rapid and efficient species identification. The practical method described in this study will facilitate peach breeding and germplasm management.
Vitis amurensis grape cultivars and hybrids are mainly used to make wines in Northeast Asia with a cold winter. Anthocyanidin glucosylation at 5-O position catalyzed by 5-O-glucosyltransferase (5GT) in grape skins is crucial for color stability of red wines. To study 5GT functions in anthocyanidin diglucosides synthesis of V. amurensis, 20 5GTs were preliminarily identified from a genome-wide characterization of the UDP-glycosyltransferase family according to the reported 5GTs, which were also performed phylogenetic and bioinformatics analysis. Two important 5GTs, Vitvi0900582.t01 and Vitvi05g01269.t01, were screened through analyses of anthocyanidin diglucosides accumulation and gene expression in berry skins of three representative grape cultivars with significant differences in anthocyanin glycosylation. Fourteen alleles of each of the 5GTs were cloned from 14 V. amurensis cultivars and hybrids as well as from V. vinifera ‘Cabernet Sauvignon’, and sequence analysis and functional prediction were performed. From three perspectives of phenotype, transcriptional level, and genotype, it has been found that the functional allele at the Vitvi0900582.t01 locus of Chr 9 played a decisive role in the synthesis of abundant anthocyanidin diglucosides in V. amurensis. In addition, the trace anthocyanidin diglucosides detected in V. vinifera ‘Cabernet Sauvignon’ were led by the functional allele at the Vitvi05g01269.t01 locus of Chr 5. This study provides preliminary data for further research on the regulatory mechanism of anthocyanidin diglucosides in the grapes with the V. amurensis pedigree to improve their wine quality in future breeding efforts.