Abstract
The posttranslational conjugation of small ubiquitin-related modifiers (SUMOs) to other proteins is involved in regulation of many processes in eukaryotic development; although its role in plant development is beginning to be dissected. Previously, we demonstrate that the siz1 mutant, impaired in a SUMO E3 ligase, showed dwarf-like shoot phenotype with accumulation of salicylic acid (SA) and the expression of nahG, a bacterial SA hydroxylase, in siz1 reduced SA level and suppressed dwarfism. Herein, we provide evidence that the SIZ1 controls cell division and elongation through regulation of SA level. siz1 plants exhibited a dwarf-like phenotype that is attributable to decreased leaf cell volume and number. Cell division and expansion defects were restored in siz1 nahG. Expression of XTH8 and XTH31, encoding xyloglucan endotransglycosylase/hydrolase, which are thought to facilitate leaf cell expansion, was down-regulated in siz1 leaves. But it was restored in siz1 nahG plants. These results indicate that SIZ1 regulates cell growth and plant development with regulation of SA accumulation. And XTH8 and XTH31 genes may be responsible for reduced leaf cell expansion.
