Overexpression of tonoplast Ca2+-ATPase in guard cells synergistically enhances stomatal opening and drought tolerance.

Stomata play a crucial role in plants by controlling water status and responding to drought stress. However, simultaneously improving stomatal opening and drought tolerance has proven to be a significant challenge. To address this issue, we employed the OnGuard quantitative model, which accurately represents the mechanics and coordination of ion transporters in guard cells. With the guidance of OnGuard, we successfully engineered plants that overexpressed the main tonoplast Ca2+-ATPase gene, ACA11, which promotes stomatal opening and enhances plant growth. Surprisingly, these transgenic plants also exhibited improved drought tolerance due to reduced water loss through their stomata. Again, OnGuard assisted us in understanding the mechanism behind the unexpected stomatal behaviors observed in the ACA11 overexpressing plants. Our study revealed that the overexpression of ACA11 facilitated the accumulation of Ca2+ in the vacuole, thereby influencing Ca2+ storage and leading to an enhanced Ca2+ elevation in response to abscisic acid. This regulatory cascade finely tunes stomatal responses, ultimately leading to enhanced drought tolerance. Our findings underscore the importance of tonoplast Ca2+-ATPase in manipulating stomatal behavior and improving drought tolerance. Furthermore, these results highlight the diverse functions of tonoplast-localized ACA11 in response to different conditions, emphasizing its potential for future applications in plant enhancement.

Arabidopsis SNARE SYP132 impacts on PIP2;1 trafficking and function in salinity stress.

In plants so-called plasma membrane intrinsic proteins (PIPs) are major water channels governing plant water status. Membrane trafficking contributes to functional regulation of major PIPs and is crucial for abiotic stress resilience. Arabidopsis PIP2;1 is rapidly internalised from the plasma membrane in response to high salinity to regulate osmotic water transport, but knowledge of the underlying mechanisms is fragmentary. Here we show that PIP2;1 occurs in complex with SYNTAXIN OF PLANTS 132 (SYP132) together with the plasma membrane H+-ATPase AHA1 as evidenced through in vivo and in vitro analysis. SYP132 is a multifaceted vesicle trafficking protein, known to interact with AHA1 and promote endocytosis to impact growth and pathogen defence. Tracking native proteins in immunoblot analysis, we found that salinity stress enhances SYP132 interactions with PIP2;1 and PIP2;2 isoforms to promote redistribution of the water channels away from the plasma membrane. Concurrently, AHA1 binding within the SYP132-complex was significantly reduced under salinity stress and increased the density of AHA1 proteins at the plasma membrane in leaf tissue. Manipulating SYP132 function in Arabidopsis thaliana enhanced resilience to salinity stress and analysis in heterologous systems suggested that the SNARE influences PIP2;1 osmotic water permeability. We propose therefore that SYP132 coordinates AHA1 and PIP2;1 abundance at the plasma membrane and influences leaf hydraulics to regulate plant responses to abiotic stress signals.