[4S01m] 09. GteX - Part 4

10:30 AM - 11:00 AM JST(1:30 AM - 2:00 AM UTC)

[4GteX-02-KL] Stomatal manipulation by phyllosphere bacteria: Toward green technologies based on plant-microbe interactions

○Rikako Hirata¹ (1. Kyoto university (Japan))

Keywords:

Plant-microbe interactions,Phyllosphere bacteria,Plant growth promotion,Pseudomonas,Arabidopsis thaliana

The GteX project aims to advance green technologies for enhanced material production and reduced CO₂ emissions. To this end, we aim to enhance plant productivity by manipulating plant-microbe interactions. Pathogenic microbes pose a serious threat to plant productivity, compromising up to 20% of global crop production. In contrast, beneficial microbes promote plant productivity by improving plant growth often under suboptimal conditions that plants face in their habitats. These beneficial plant-microbe interactions have been studied primarily in root-centered belowground parts of plants. Consequently, our understanding on beneficial interactions in leaf-dominated aboveground parts of plants known as the phyllosphere remains limited. In this talk, I will present our effort to elucidate both detrimental and beneficial plant-bacteria interactions through stomata, which are microscopic pores found specifically in the phyllosphere. Plants control stomatal pore size to increase CO₂ uptake for photosynthesis while reducing water loss. In addition, stomata serve as a key defense layer, as plants close them to restrict the entry of pathogenic bacteria into leaf tissues. As a countermeasure, the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 (Pto) produces the phytotoxin coronatine. I discovered that coronatine exploits a plant gene regulatory mechanism to reopen stomata. While the ability to open stomata has been reported exclusively in pathogenic bacteria, I recently isolated a beneficial stomata-opening bacterium, Pseudomonas paralactis (Ppr). Ppr colonizes plant leaf surface and promotes plant growth. Notably, delayed stomatal opening at dawn is known to limit efficient CO₂ uptake and photosynthesis. Interestingly, however, I found that Ppr-colonized plants open stomata before dawn. Comparative genomics in combination with molecular genetic analyses revealed that Ppr opens stomata via a mechanism distinct from that of Pto. Moreover, the culture supernatant of Ppr retained stomata-opening activity even after heat treatment, suggesting that heat-resistant metabolites secreted by Ppr function as stomata-opening factors. These findings provide a foundation for improving plant productivity by manipulating stomatal responses to both pathogenic and beneficial phyllosphere bacteria.