Multiple Roles of the Plasma Membrane H(+)-ATPase and Its Regulation

PP2C.D phosphatase SAL1 positively regulates aluminum resistance via restriction of aluminum uptake in rice

Aluminum (Al) toxicity represents a primary constraint for crop production in acidic soils. Rice (Oryza sativa) is a highly Al-resistant species; however, the molecular mechanisms underlying its high Al resistance are still not fully understood. Here, we identified SAL1 (SENSITIVE TO ALUMINUM 1), which encodes a plasma membrane (PM)-localized PP2C.D phosphatase, as a crucial regulator of Al resistance using a forward genetic screen. SAL1 was found to interact with and inhibit the activity of PM H+-ATPases, and mutation of SAL1 increased PM H+-ATPase activity and Al uptake, causing hypersensitivity to internal Al toxicity. Furthermore, knockout of NRAT1 (NRAMP ALUMINUM TRANSPORTER 1) encoding an Al uptake transporter in a sal1 background rescued the Al-sensitive phenotype of sal1, revealing that coordination of Al accumulation in the cell, wall and symplasm is critical for Al resistance in rice. By contrast, we found that mutations of PP2C.D phosphatase-encoding genes in Arabidopsis (Arabidopsis thaliana) enhanced Al resistance, which was attributed to increased malate secretion. Our results reveal the importance of PP2C.D phosphatases in Al resistance and the different strategies used by rice and Arabidopsis to defend against Al toxicity.

Plant Plasma Membrane Proton Pump: One Protein with Multiple Functions

In plants, the plasma membrane proton pump (PM H⁺-ATPase) regulates numerous transport-dependent processes such as growth, development, basic physiology, and adaptation to environmental conditions. This review explores the multifunctionality of this enzyme in plant cells. The abundance of several PM H⁺-ATPase isogenes and their pivotal role in energizing transport in plants have been connected to the phenomena of pleiotropy. The multifunctionality of PM H⁺-ATPase is a focal point of numerous studies unraveling the molecular mechanisms of plant adaptation to adverse environmental conditions. Furthermore, PM H⁺-ATPase is a key element in plant defense mechanisms against pathogen attack; however, it also functions as a target for pathogens that enable plant tissue invasion. Here, we provide an extensive review of the PM H⁺-ATPase as a multitasking protein in plants. We focus on the results of recent studies concerning PM H⁺-ATPase and its role in plant growth, physiology, and pathogenesis.

Promotion and Upregulation of a Plasma Membrane Proton-ATPase Strategy: Principles and Applications

Plasma membrane proton-ATPase (PM H+-ATPase) is a primary H+ transporter that consumes ATP in vivo and is a limiting factor in the blue light-induced stomatal opening signaling pathway. It was recently reported that manipulation of PM H+-ATPase in stomatal guard cells and other tissues greatly improved leaf photosynthesis and plant growth. In this report, we review and discuss the function of PM H+-ATPase in the context of the promotion and upregulation H+-ATPase strategy, including associated principles pertaining to enhanced stomatal opening, environmental plasticity, and potential applications in crops and nanotechnology. We highlight the great potential of the promotion and upregulation H+-ATPase strategy, and explain why it may be applied in many crops in the future.

Panicle Apical Abortion 3 Controls Panicle Development and Seed Size in Rice

BACKGROUND

In rice, panicle apical abortion is a common phenomenon that usually results in a decreased number of branches and grains per panicle, and consequently a reduced grain yield. A better understanding of the molecular mechanism of panicle abortion is thus critical for maintaining and increasing rice production.

RESULTS

We reported a new rice mutant panicle apical abortion 3 (paa3), which exhibited severe abortion of spikelet development on the upper part of the branches as well as decreased grain size over the whole panicle. Using mapping-based clone, the PAA3 was characterized as the LOC_ Os04g56160 gene, encoding an H⁺-ATPase. The PAA3 was expressed highly in the stem and panicle, and its protein was localized in the plasma membrane. Our data further showed that PAA3 played an important role in maintaining normal panicle development by participating in the removal of reactive oxygen species (ROS) in rice.

CONCLUSIONS

Our studies suggested that PAA3 might function to remove ROS, the accumulation of which leads to programmed cell death, and ultimately panicle apical abortion and decreased seed size in the paa3 panicle.

Plasma membrane H+-ATPase overexpression increases rice yield via simultaneous enhancement of nutrient uptake and photosynthesis

Nitrogen (N) and carbon (C) are essential elements for plant growth and crop yield. Thus, improved N and C utilisation contributes to agricultural productivity and reduces the need for fertilisation. In the present study, we find that overexpression of a single rice gene, Oryza sativa plasma membrane (PM) H+-ATPase 1 (OSA1), facilitates ammonium absorption and assimilation in roots and enhanced light-induced stomatal opening with higher photosynthesis rate in leaves. As a result, OSA1 overexpression in rice plants causes a 33% increase in grain yield and a 46% increase in N use efficiency overall. As PM H+-ATPase is highly conserved in plants, these findings indicate that the manipulation of PM H+-ATPase could cooperatively improve N and C utilisation, potentially providing a vital tool for food security and sustainable agriculture.

Oryza sativa H+-ATPase (OSA) is Involved in the Regulation of Dumbbell-Shaped Guard Cells of Rice

The stomatal apparatus consists of a pair of guard cells and regulates gas exchange between the leaf and atmosphere. In guard cells, blue light (BL) activates H(+)-ATPase in the plasma membrane through the phosphorylation of its penultimate threonine, mediating stomatal opening. Although this regulation is thought to be widely adopted among kidney-shaped guard cells in dicots, the molecular basis underlying that of dumbbell-shaped guard cells in monocots remains unclear. Here, we show that H(+)-ATPases are involved in the regulation of dumbbell-shaped guard cells. Stomatal opening of rice was promoted by the H(+)-ATPase activator fusicoccin and by BL, and the latter was suppressed by the H(+)-ATPase inhibitor vanadate. Using H(+)-ATPase antibodies, we showed the presence of phosphoregulation of the penultimate threonine in Oryza sativa H(+)-ATPases (OSAs) and localization of OSAs in the plasma membrane of guard cells. Interestingly, we identified one H(+)-ATPase isoform, OSA7, that is preferentially expressed among the OSA genes in guard cells, and found that loss of function of OSA7 resulted in partial insensitivity to BL. We conclude that H(+)-ATPase is involved in BL-induced stomatal opening of dumbbell-shaped guard cells in monocotyledon species.