The interactions of PhSPL17 and PhJAZ1 mediate the on- and off-year moso bamboo (Phyllostachys heterocycla) resistance to the Pantana phyllostachysae larval feeding

BACKGROUND The immunity of moso bamboo (Phyllostachys heterocycle) to insect defoliator outbreaks differs between on-years to off-years; however, the underlying genetic mechanisms remain unknown. In this study, the genetic relationships of functional genes conferring pest resistance were investigated. RESULTS PhJAZ1 (Phyllostachys heterocycla JASMONATE ZIM-domain protein 1) exhibited the highest enrichment and was expressed at higher levels in the leaves of on-year bamboo plants compared with off-year, whereas the expression of PhSPL17 (Phyllostachys heterocycla SQUAMOSA Promoter binding protein-Like 17) showed the reverse pattern. The expression pattern of PhJAZ1 differed in on- and off-year bamboo (i.e., decreasing in the off-year with no obvious change in the on-year) after feeding by Pantana phyllostachysae (lepidopteran caterpillar of moso bamboo). Due to the lack of a genetic transformation system, the model plant Arabidopsis was used for the investigation of the genetic relationships between PhJAZ1 and PhSPL17. Overexpression of the PhJAZ1 protein in Arabidopsis showed a negative impact on the survival ratio and weight of third-instar Helicoverpa armigera (Arabidopsis leaf-feeding lepidopteran caterpillar). Transcriptional suppression of PhJAZ1 by PhSPL17 was observed, which was able to reveal the reverse expression pattern of PhJAZ1 and PhSPL17. CONCLUSION Together, these results suggest that on- and off-years (leaf age) regulate the expression of PhSPL17, which negatively regulates the expression of PhJAZ1 to generate differential response to Jasmonate. This study is the first to detail the genetic connection between leaf age and Jasmonate response in moso bamboo and provides a foundation for further pest control via the genetic breeding of moso bamboo. (c) 2019 Society of Chemical Industry