College of Plant Science and Technology of Huazhong Agricultural University， National Research Center of Rapeseed Engineering and Technology， Wuhan 430070
Foundation projects： China Agriculture Research System of MOF and MARA （CARS-12）； National Key Research and Development Program of China （2017YFD0101702）
Leaf-color mutants are crucial germplasms for deciphering the mechanisms of pigment metabolism and chloroplast development. In this study， to uncover the mechanisms of temperature-sensitive albino phenotype in Brassica napus， the physiological assessment and transcriptome analysis were performed in two resynthesized B. napus inbred lines， the white-leaf line W7105 and its green-leaf sibling line G7097. Under low temperature in field conditions， in albino leaves of W7105， the chlorophyll and carotenoid content were dramatically decreased and chloroplast structure was abnormal. Compared with green leaves， albino leaves showed significantly lower net photosynthetic rate （Pn） and significantly higher intercellular CO2 concentration （Ci）. Transcriptome analysis of leaves at three different developing stages was performed in G7097 and W7105 lines. After pairwise comparisons， a total of 1532 differentially expressed genes （DEGs） associated with leaf color phenotype were identified， including 540 and 992 genes that were up-regulated and down-regulated， respectively. GO and KEGG enrichment analysis showed that the up-regulated DEGs in albino leaves of W7105 were significantly enriched in proteasome， translation process， carbohydrate and energy metabolism pathways； while the down-regulated DEGs were significantly enriched in chloroplasts， photosynthesis and electron transport chain. Moreover， several DEGs in chlorophyll and carotenoid biosynthesis were significantly down-regulated in albino leaves， suggesting that chlorophyll and carotenoid metabolisms were also impaired. Collectively， these findings provide references for further delimiting the candidate genes and uncovering the molecular mechanisms of albino leaves in B. napus.