Myotubularins, PtdIns5P, and ROS in ABA-mediated stomatal movements in dehydrated Arabidopsis seedlings

Abstract

Myotubularins (MTMs) are lipid phosphoinositide 3-phosphate phosphatases and the product of their enzyme activity – phosphoinositide 5-phosphate (PtdIns5P) – functions as a signalling molecule in pathways involved in membrane dynamics and cell signalling. Two Arabidopsis genes, AtMTM1 and AtMTM2, encode enzymatically active phosphatases but although AtMTM1 deficiency results in increased tolerance to dehydration stress and a decrease in cellular PtdIns5P, the role of AtMTM2 is less clear, as it does not contribute to the PtdIns5P pool upon dehydration stress. Here we analysed the involvement of AtMTM1, AtMTM2 and PtdIns5P in the response of Arabidopsis seedlings to dehydration stress/ABA, and found that both AtMTM1 and AtMTM2 were involved but affected oppositely stomata movement and the accumulation of reactive oxygen species (ROS, e.g. H2O2). Acting as a secondary messenger in the ABA-induced ROS production in guard cells, PtdIns5P emerges as an evolutionarily conserved signalling molecule that calibrates cellular ROS under stress. We propose the biological relevance of the counteracting AtMTM1 and AtMTM2 activities is to balance the ABA-induced ROS accumulation and cellular homeostasis under dehydration stress.

Defence‐related priming and responses to recurring drought: Two manifestations of plant transcriptional memory mediated by the ABA and JA signalling pathways

“…This conclusion is supported by the fact that diverse phytohormones mediate stress signalling pathways and TFs coregulate (both synergistically and antagonistically) overlapping gene sets (Ahmad et al, ; Bostock, Pye, & Roubtsova, ; Huang et al, ; Prasch & Sonnewald, ; Rieman et al, ). Moreover, hormone‐activated signalling pathways raise the levels of other signalling molecules (reactive oxygen species (ROS) and phosphoinositides) that function as secondary messengers for the networks that close stomata and affect cellular homeostasis and gene expression (Balla, ; Choi, Lee, Jeon, Staiger, & Lee, ; Deng et al, ; Ding et al, ; Ding, Ndamukong, Zhao, et al, ; Locato et al, ; Murata, Mori, & Munemasa, ; Nagpal, Hassan, Ndamukong, Avramova, & Baluška, ; Ndamukong, Jones, Lapko, Divecha, & Avramova, ; Turkan, ; Wang & Song, ). The measured transcript levels for any stress responding gene, therefore, represent the compound effect from the activity of complex signalling networks.…”

Understanding and exploiting autophagy signaling in plants

“…Both pathways are possible in plants as PIKfyve kinase and myotubularin phosphatases are present in Arabidopsis [ 47 , 48 ]. Arabidopsis myotubularins AtMTM1 and AtMTM2 control vesicular trafficking between the ER and cis -Golgi [ 48 ], and AtMTM1 controls PI5P levels associated with ROS–ABA-mediated stomatal movements [ 49 ].…”