[1S01e] 10. ASPIRE - Part 3

4:55 PM - 5:05 PM JST(7:55 AM - 8:05 AM UTC)

[1ASPR-18] Regulatory mechanisms of BLUS1 expression in blue light-dependent stomatal opening for improving plant water use efficiency

○Ayuri Yamaguchi¹ (1. Yamaguchi University (Japan))

Keywords:

stomata,blue light,water use efficiency

Stomata, which consist of a pair of guard cells, open in response to blue light, facilitating CO2 uptake for photosynthetic carbon assimilation and water loss through transpiration. Blue light is perceived by the blue light receptor kinase phototropins, which transduce the signal through BLUS1 phosphorylation, thereby activating the plasma membrane H+-ATPase. BLUS1 is an essential protein kinase for blue light-dependent stomatal opening, and its expression is restricted to guard cells. It has been reported that the blus1 mutant exhibits stomatal opening approximately half that of the wild type, while maintaining a comparable CO2 assimilation rate. Therefore, the strict control of BLUS1 expression may enhance plant water use efficiency; however, the regulatory mechanisms underlying its expression have yet to be clarified. In this study, we focused on SCAP1, a guard cell-specific Dof-type transcription factor that is involved in guard cell maturation and stomatal functionalization, and examined its possible role in BLUS1 expression and stomatal opening. We found that BLUS1 expression was reduced in guard cell protoplasts of the scap1 mutant, and that blue light-dependent activation of plasma membrane H+-ATPase as well as stomatal opening were impaired. Furthermore, an in vitro pull-down assay revealed that SCAP1 directly binds to the upstream regulatory region of BLUS1. During the internship, we collaborated with Prof. Diwakar Shukla from the University of Illinois, performed in silico analyses to predict the SCAP1-binding sites within the upstream regulatory region of BLUS1, and identified a candidate cis-element. An in vitro pull-down assay using a mutated BLUS1 sequence confirmed that SCAP1 binding depends on this cis-element. Taken together, these results suggest that SCAP1 directly regulates BLUS1 expression in guard cells, thereby promoting blue light-dependent stomatal opening.