Chlorophyll a/b-binding protein gene AcLhcb1.1 promotes chlorophyll accumulation and improves cold stress resistance in kiwifruit

Chlorophyll degradation coupled with the accumulation of other pigments during fruit ripening result in different colors in kiwifruit flesh. Light- harvesting chlorophyll a/b binding proteins (Lhc) play crucial roles in photosynthesis and chlorophyll metabolism. However their specific functions in kiwifruit fruit coloration remain poorly understood. Here, we identified 31 Lhcs family members from the kiwifruit genome, most of which possess cis-acting elements in response to light, low temperature and abscisic acid in their promoters. Through transcriptome profile analysis, AcLhcb1.1 was screened positively associated with flesh coloration. AcLhcb1.1 displayed lower expression levels in the yellow-fleshed variety ‘Jinshi 1’ but higher expression levels in the green-fleshed variety ‘White’. Moreover, overexpression of AcLhcb1.1 in tobacco and kiwifruit resulted in a significant increase in leaf chlorophyll content compared with wild type (WT), accompanied by down-regulated expression of chlorophyll degradation genes AcPPH and AcPAO. In addition, transgenic kiwifruit plants exhibited reduced malondialdehyde content and relative electrolyte leakage compared to WT when exposed to low temperature, and higher antioxidant enzyme activities of SOD, CAT, and POD. These results suggest that AcLhcb1.1 plays a vital role not only in chlorophyll maintenance but also enhancing resistance against low temperature stress.