Roles of plasma membrane proton ATPases AHA2 and AHA7 in normal growth of roots and root hairs in Arabidopsis thaliana

Abstract

Plasma membrane H+‐ATPase pumps build up the electrochemical H+ gradients that energize most other transport processes into and out of plant cells through channel proteins and secondary active carriers. In Arabidopsis thaliana, the AUTOINHIBITED PLASMA MEMBRANE H+‐ATPases AHA1, AHA2 and AHA7 are predominant in root epidermal cells. In contrast to other H+‐ATPases, we find that AHA7 is autoinhibited by a sequence present in the extracellular loop between transmembrane segments 7 and 8. Autoinhibition of pump activity was regulated by extracellular pH, suggesting negative feedback regulation of AHA7 during establishment of an H+ gradient. Due to genetic redundancy, it has proven difficult to test the role of AHA2 and AHA7, and mutant phenotypes have previously only been observed under nutrient stress conditions. Here, we investigated root and root hair growth under normal conditions in single and double mutants of AHA2 and AHA7. We find that AHA2 drives root cell expansion during growth but that, unexpectedly, restriction of root hair elongation is dependent on AHA2 and AHA7, with each having different roles in this process.

Plasma membrane H+-ATPases sustain pollen tube growth and fertilization

“…We confirmed the H + pump activity of each of these proteins by heterologously expressing cDNA containing their coding region in the yeast strain RS-72, in which the native proton pump PMA1 is under the control of a galactose-inducible promoter 22 . This strain can only grow in the absence of galactose when a functional plasma membrane H + pump is expressed.…”

“…A likely explanation is that one or more additional AHA isoforms is involved in pollen tube growth during the early growth phases. AHA7 is also expressed in pollen tubes 22 , but at a much lower level than AHA6, AHA8, and AHA9 ( Supplementary Fig. 1).…”

Nitrogen Uptake in Plants: The Plasma Membrane Root Transport Systems from a Physiological and Proteomic Perspective

“…Phylogeny analysis of Arabidopsis PM H + -ATPase isoforms, named AHA (Autoinhibited H + -ATPase) recognizes five subfamilies. One group contains AHA4 and AHA11, the second one clusters isoforms similar to AHA1 (AHA2, AHA3, AHA5, AHA12), the third and the fourth only consist of AHA10 and AHA7, respectively, and the last group comprises AHA6, AHA8, and AHA9 [ 152 , 153 ]. Unexpectedly, AHA10-like isoforms target the tonoplast where they possibly assemble as hetero-oligomers [ 154 , 155 ].…”

Evidence for multiple receptors mediating RALF‐triggered Ca2+ signaling and proton pump inhibition

“…A balance between active H + pumping out of the cell by plasma membrane‐localized H + ‐ATPases and passive H + efflux or influx maintains cytoplasmic pH homeostasis (Demaurex, 2002). We recently demonstrated a role for the membrane H + ‐ATPases AHA2 and AHA7 in root hair development (Hoffmann et al ., 2019). There is growing recognition that localized pH changes may occur together with cytosolic Ca 2+ transients as coordinated signaling cues (Behera et al ., 2018).…”