RESUMO
The sugar transporter (ST) plays an important role in plant growth, development and fruit quality. In this study, a total of 75 ST genes were identified in the pear (Pyrus bretschneideri Rehd) genome based on systematic analysis. Furthermore, all ST genes identified were grouped into eight subfamilies according to conserved domains and phylogenetic analysis. Analysis of cis-regulatory element sequences of all ST genes identified the MYBCOREATCYCB1 promoter in sucrose transporter (SUT) and monosaccharide transporter (MST) genes of pear, while in grape it is exclusively found in SUT subfamily members, indicating divergent transcriptional regulation in different species. Gene duplication event analysis indicated that whole-genome duplication (WGD) and segmental duplication play key roles in ST gene amplification, followed by tandem duplication. Estimation of positive selection at codon sites of ST paralog pairs indicated that all plastidic glucose translocator (pGlcT) subfamily members have evolved under positive selection. In addition, the evolutionary history of ST gene duplications indicated that the ST genes have experienced significant expansion in the whole ST gene family after the second WGD, especially after apple and pear divergence. According to the global RNA sequencing results of pear fruit development, gene expression profiling showed the expression of 53 STs. Combined with quantitative real-time PCR (qRT-PCR) analysis, two polyol/monosaccharide transporter (PLT) and three tonoplast monosaccharide transporter (tMT) members were identified as candidate genes, which may play important roles in sugar accumulation during pear fruit development and ripening. Identification of highly expressed STs in fruit is important for finding novel genes contributing to enhanced levels of sugar content in pear fruit.
Assuntos
Evolução Molecular , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Proteínas de Membrana Transportadoras/genética , Família Multigênica , Pyrus/genética , Motivos de Aminoácidos , Sequência de Aminoácidos , Sequência de Bases , Cromossomos de Plantas/genética , Códon/genética , Sequência Conservada/genética , Éxons/genética , Frutas/genética , Duplicação Gênica , Perfilação da Expressão Gênica , Íntrons/genética , Proteínas de Membrana Transportadoras/metabolismo , Dados de Sequência Molecular , Filogenia , Regiões Promotoras Genéticas/genética , Estrutura Terciária de Proteína , Reação em Cadeia da Polimerase em Tempo Real , Reprodutibilidade dos Testes , Seleção Genética , Transcrição GênicaRESUMO
MAIN CONCLUSION: Comparative and association analyses of the proteome and transcriptome for pear fruit development were conducted for the first time in this study. Pear fruit development involves complex physiological and biochemical processes, but there is still little knowledge available at proteomic and transcriptomic levels, which would be helpful for understanding the molecular mechanisms of fruit development and quality in pear. In our study, three important stages, including early development (S4-22), middle development (S6-27), and near ripening (S8-30), were investigated in 'Dangshansuli' by isobaric tags for relative and absolute quantitation (iTRAQ) labeling technology, identifying a total of 1,810 proteins during pear fruit development. The association analysis of proteins and transcript expression revealed 1,724, 1,722, and 1,718 associated proteins identified in stages S4-22, S6-27, and S8-30, respectively. A total of 237, 318, and 425 unique proteins were identified as differentially expressed during S4-22 vs S6-27, S6-27 vs S8-30, S4-22 vs S8-30, respectively, and the corresponding correlation coefficients of the overall differentially expressed proteins and transcripts data were 0.6336, 0.4113, and 0.7049. The phenylpropanoid biosynthesis pathway, which is related to lignin formation of pear fruit, was identified as a significantly enriched pathway during early stages of fruit development. Finally, a total of 35 important differentially expressed proteins related to fruit quality were identified, including three proteins related to sugar formation, seven proteins related to aroma synthesis, and sixteen proteins related to the formation of lignin. In addition, qRT-PCR verification provided further evidence to support differentially expressed gene selection. This study is the first to reveal protein and associated mRNA variations in pear during fruit development and quality conformation, and identify key genes and proteins helpful for future functional genomics studies, and provides gene resources for improvement of pear quality.