Recently, Prof. Ming-Yi Bai's group, from the School of Life Science, made new progress in Sugar and TOR signaling promote guard cell starch degradation throughβ-AMYLASE activity.Related results have been published on the international top journalThe Plant Cellentitled “TOR promotes guard cell starch degradation by regulating the activity ofβ-AMYLASE1 in Arabidopsis”. The first author is Dr. Chao Han from the School of Life Science. Prof. Ming-Yi Bai is the corresponding authors.

Stomata, which plays a major role in controlling gas exchange between plants and the atmosphere, is composed by two specific functional guard cells. Starch in guard cells is present at night and degrades within 1 hour light exposure to promote stomatal opening. This transitory starch breakdown in guard cells produces glucose, but not malate, maintaining the cytoplasmic sugar pool and inducing stomatal opening. In this study, the authors proved that the plants grown under short photoperiod or weak light intensity without sucrose exhibited decreased guard cell starch levels and an impaired stomatal opening phenotype. Sucrose supplementation recovered the light-triggered degradation of guard cell starch and stomatal opening of plants grown under short photoperiod or weak light intensity conditions.

Target of rapamycin (TOR) is an evolutionarily conserved master regulator that modulates nutrient status and energy signaling to promote cell proliferation and growth in all eukaryotes. In this study, the author showed that inactivation of TOR impaired guard cell starch degradation, stomatal opening and conductance. TOR promotesβ-AMYLASE1(BAM1) expression by stabilize BZR1, a key transcription factor in brassinosteroid signaling. Besides, TOR promote BAM1 protein stability by autophagy and proteasome pathway. TOR dependent phosphorylation on BAM1 are also important for BAM1 protein stability.

This work illuminates the mechanism of TOR regulating starch degradation and opening, which provides a new aspect on “starch-sugar hypothesis for stomata opening” and give a new direction in this field in future.

This work was funded by Shandong Province Agricultural Improved Variety Project, the National Natural Science Foundation of China, Shandong Province Natural Science Foundation and the Young Scholars Program of Shandong University.

The links of papers: https://academic.oup.com/plcell/advance-article/doi/10.1093/plcell/koab307/6468628