Transcriptome profiling reveals differentially expressed genes associated with wizened flower bud formation in Chinese pear (Pyrus bretschneideri Rehd.)

Flower buds are very important for pear yield; non-germinated flower buds become wizened and drop from the branch, reducing pear production. However, little research has focused on the study of wizened flower bud (WB) formation in spring. In order to elucidate the mechanism of WB formation in pear, physiological indices relating to plant hormones and antioxidases were measured. We found that activities of peroxidase (POD) and superoxide dismutase (SOD) were higher and lower, respectively, in WBs than in normal flower buds (NBs). The contents of indole acetic acid (IAA), gibberellin (GA), and cytokinin (CTK) were lower in WBs, while the level of addition of abscisic acid (ABA) was higher in WBs than in NBs. Differentially expressed genes (DEGs) were surveyed between WBs and NBs. In total, 23 DEGs relating to POD and SOD were detected from GO (Gene Ontology) enrichment, and 29 DEGs associated with plant hormone biosynthesis were found from the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway. Notably, the expression patterns of these 52 genes were consistent with variations of antioxidase activities or hormone contents. Because POD and SOD are stress-response enzymes, the differences in POD and SOD activities between NBs and WBs indicated that WB formation in pear could result from ambient environmental stresses that influence expression levels of hormone biosynthesis genes.