Genome-wide transcriptomic analysis during rhizome development of ginger (Zingiber officinale Roscoe.) reveals hormone and transcriptional regulation involved in cellulose production

Abstract

Ginger is a popular vegetable crop primarily consumed in Chongqing and Sichuan, China. The rhizome becomes tough and fibrous rapidly with the tissue maturation, resulting in loss of edible quality. To characterize biochemical and molecular mechanisms of rhizome texture modification, we investigated the changes of the cell wall components, hormones and transcriptome profiles during rhizome development. With rhizomes maturation, the contents of cellulose and hemicellulose increased gradually, and no obvious change was observed in lignin accumulation. The levels of ABA and cytokinin exhibited a gradual decline during maturation of ginger rhizome, which were negatively correlated with cellulose content, while GA3 displayed an increasing trend and a positive correlation with cellulose production. Transcriptomic analysis identified candidate genes involved in cellulose biosynthesis including cellulose synthase subunit A (CesA) genes, hormone metabolism and signaling genes, and NAC-MYB-based transcription factors. Further analysis demonstrated ZoCESA7, ZoNAC16 and ZoMYB37/39/41, homologs of AtCESA7, AtVND6/7 and AtMYB46/83, respectively, positively correlated with cellulose contents, whereas ZoNAC3/9/13 and ZoMYB7/11/18, homologs of AtVND6/7 and AtMYB4, respectively, negatively correlated with cellulose levels, indicating their involvements in cellulose synthesis during rhizome development. These findings provide new insight into molecular events of cellulose accumulation mainly mediated by hormones and transcription factors in ginger rhizomes.