Transcriptome Analysis of Brassica napus Wax-Deficient Mutant Revealed the Dynamic Regulation of Leaf Wax Biosynthesis is Associated with Basic pentacysteine 6

Abstract

Wax is a protective layer through which plants directly contact the environment and it plays an important role in plant responses to biotic and abiotic stresses. The biosynthesis of wax is a dynamic process that occurs over different growth stages. Although wax biosynthesis has been well studied, there are limited reports on how plants regulate wax synthesis at different developmental stages. In this study, we identified a wax-deficient mutant (wad) in rapeseed (Brassica napus L.). The wad true leaf was shiny at the young stage (wad-y) but recovered at the mature stage (wad-m) and further analyses indicated that wax biosynthesis was blocked in wad-y leaves. The gene expression patterns of wild-type (WT) during the young (WT-y) and mature (WT-m) stages, wad-y and wad-m were monitored using RNA sequencing. The Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation showed that differentially expressed genes (DEGs) were gathered in the fatty acid elongation pathway. These genes were down-regulated in wad-y and returned to normal levels in wad-m, indicating that the changes in fatty acid elongation genes' expression lead to dynamic changes in wax. Moreover, a transcription factor-enrichment analysis showed that BASIC PENTACYSTEINE 6 (BPC6) is the key regulator affecting fatty acid elongation. Taken together, our study showed BPC6 potentially affects the biosynthesis of wax during different developmental stages by regulating the elongation of fatty acid chains. This study will provide new insights into the regulation of wax biosynthesis during different developmental stages of rapeseed