Transcriptional Regulation Of Loquat Fruit Lignification By MYB

Loquat is rosaceae perennial woody fruit tree and its fruits are sensitive to low temperature (0℃) with chilling injury induced lignification. The present research investigated transcriptional regulatory mechanisms of EjMYB on loquat fruit lignification, which provide scientific basis for improving storage and logistics system.The main results are as followed:1. EjMYB genes isolation and characterization.23EjMYB members were isolated with RNA-seq and homologous clone, among which two lignin-related candidate genes EjMYB1and EjMYB2were classed as activator and repressor, respectively, with phylogenetic and alignment analysis. EjMYB1and EjMYB2were located to nucleus and had trans-activation abilities in yeast, and the activation motif was at the C-terminate, except for R2R3and EAR motif.2. EjMYBl and EjMYB2were involved in chilling injury induced fruit lignification. The genes responded differently to low temperature, with EjMYBl induced and EjMYB2inhibited by0℃. Heat treatment (HT) and low temperature condition (LTC) would alleviate lignification and prohibited EjMYBl expression. In contrast, repressor EjMYB2was negative correlated with fruit lignification. These results indicate that EjMYBl and EjMYB2were positive and negative regulator for fruit lignification, respectively. LTC alleviated chilling injury and lignification through regulating both EjMYBl and EjMYB2, while HT specifically regulated EjMYBl.3. EjMYBl and EjMYB2participated in lignification transcriptional regulation. EjMYBl activated promoters of lignin biosynthesis genes from Arabidopsis using dual luciferase assay. Similarly, EjMYBl also activated lignin biosynthesis gene promoters of loquat, such as EjPALl, Ej4CLl and Ej4CL5. Yeast one hybrid and promoter deletion analysis indicated that EjMYBl and EjMYB2regulated target promoters via recognizing the AC-elements in promoter region, meanwhile EjMYB2may recognize different AC-elements or compete the same AC-element with EjMYBl. Transient over-expression of EjMYBl in tobacco leaves triggered lignin biosythesis, which were prohibited by EjMYB2.