A comprehensive view of expression profiles dynamics of capsaicinoid biosynthesis-related genes during pepper fruit development and under MeJA treatment

摘要

Capsaicinoids are a group of secondary plant metabolites which are synthesized and accumulated only in the fruits of peppers ( Capsicum annuum L.). In this paper, the fruits of nadao chili peppers were used as experiment materials and the mechanism of capsaicinoid biosynthesis was studied. HPLC studies revealed that capsaicinoid accumulation in the developing fruits initially occurred at 24 days after pollination (DAP), was increasing at 36 DAP, and peaked at 48 DAP. Eleven genes that encoded enzymes involved in capsaicinoid biosynthesis were isolated and characterized. Gene expression with quantitative reverse-transcription polymerase chain reaction analysis demonstrated that capsaicin synthase ( CaCS ) was expressed only in the placenta of the fruit, while the other ten genes were expressed in all tissues tested, with nine of the eleven genes (with the exception of cinnamic acid-4-hydroxylase [ CaCa4H ] and p -coumaric acid-3-hydroxylase [ CaCa3H ]) being strongly expressed in placenta tissue. Spatial expression analysis demonstrated that the 11 genes could be grouped into four categories, based on the patterns of relative expression of the genes during fruit development. Category I contained two genes, which displayed a bell-shaped expression pattern, with peak expression at 24 DAP. Category II contained five genes, the expression of which increased steadily from 0 to 36 DAP, peaking at 36 DAP. Category III comprises two genes, expression of which peaked at 48 DAP. Category IV consists of two genes, which were not expressed from 0 to 12 DAP, but then showed a high level of expression at 36 and 48 DAP. Treatment of the developing fruit with methyl jasmonate (MeJA) resulted in upregulation of the expression of each of the 11 genes. These results provide the first information on capsaicinoid biosynthesis and regulation during pepper fruit development.