The 30th International Conference on Arabidopsis Research (ICAR 2019)

408 / 2019-01-11 13:56:11

Brassinosteroid and hydrogen peroxide interdependently induce stomatal opening by promoting starch degradation

Brassinosteroid,Hydrogen peroxide,starch

Plenary track > Hormones

Starch is the major storage glucose polymer in plants and functions in buffering carbon and energy availability for plant fitness with challenging environmental conditions. The timing and extent at which starch degradation occurs appear to be determined by diverse hormonal and environmental signals. However, the understanding of the regulation of starch metabolism is fragmentary. Here, we demonstrate that the plant steroid hormone brassinosteroid (BR) and the redox signal hydrogen peroxide (H2O2) induce starch breakdown in guard cells to promote stomatal opening. BR deficient mutant det2 and insensitive mutant bri1-116 both accumulated high levels of starch in guard cells and impaired the stomatal opening. Whereas the gain-of-function mutant bzr1-1D partially suppressed the high accumulated starch phenotype in det2 and bri1-116, thereby promoting stomatal opening. BZR1 interacts with HRT2 to induce starch turnover by promoting the expression of β-AMYLASE1 (BAM1), which is responsible for the majority of starch degradation in guard cells. In turn, H2O2 induces the oxidation of BZR1 and enhances the interaction between BZR1 with HRT2 to increase BAM1 transcription and promote starch degradation in guard cells. A mutation in BAM1 leads to starch accumulation in guard cells and reduce the effects of BR and H2O2 on stomatal opening. Overall, the present study uncovers the critical roles of BR and H2O2 in the regulation of starch metabolism and stomatal opening.