Expression analysis of two gene subfamilies encoding the plasma membrane H⁺‐ATPase in Nicotiana plumbaginifolia reveals the major transport functions of this enzyme

Abstract

Summary The plasma membrane H+‐ATPase couples ATP hydrolysis to proton transport, thereby establishing the driving force for solute transport across the plasma membrane. In Nicotiana plumbaginifolia, this enzyme is encoded by at least nine pma (plasma membrane H+‐ATPase) genes. Four of these are classified into two gene subfamilies, pma1‐2‐3 and pma4, which are the most highly expressed in plant species. We have isolated genomic clones for pma2 and pma4. Mapping of their transcript 5′ end revealed the presence of a long leader that contained small open reading frames, regulatory features typical of other pma genes. The gusA reporter gene was then used to determine the expression of pma2, pma3 and pma4 in N. tabacum. These data, together with those obtained previously for pma1, led to the following conclusions. (i) The four pma–gusA genes were all expressed in root, stem, leaf and flower organs, but each in a cell‐type specific manner. Expression in these organs was confirmed at the protein level, using subfamily‐specific antibodies. (ii) pma4–gusA was expressed in many cell types and notably in root hair and epidermis, in companion cells, and in guard cells, indicating that in N. plumbaginifolia the same H+‐ATPase isoform might be involved in mineral nutrition, phloem loading and control of stomata aperture. (iii) The second gene subfamily is composed, in N. plumbaginifolia, of a single gene (pma4) with a wide expression pattern and, in Arabidopsis thaliana, of three genes (aha1, aha2, aha3), at least two of them having a more restrictive expression pattern. (iv) Some cell types expressed pma2 and pma4 at the same time, which encode H+‐ATPases with different enzymatic properties.

Adaptation of H+-Pumping and Plasma Membrane H+ ATPase Activity in Proteoid Roots of White Lupin under Phosphate Deficiency

“…Therefore, it is likely that in active proteoid roots, an enhanced expression of a special isoform (or isoforms) of plasma membrane H ϩ ATPase is induced to meet the high demand of the cells to extrude H ϩ . Such a tissue-, organ-, or cell-specific expression of isoforms of H ϩ ATPase has been reported by a number of investigations (DeWitt et al, 1991;Michelet et al, 1994;Moriau et al, 1999) and summarized as a "tissue-specific expression model" in which enzymatically equivalent enzymes are expressed in different cells by promoters providing controlled expression levels ideally suited for a cell's particular needs (Palmgren and Harper, 1999).…”

Inventory of the Superfamily of P-Type Ion Pumps in Arabidopsis

“…We can expect rapid advances in our understanding of the function of P-type pumps with the combination of physiological and molecular genetic approaches in the coming years. Reporter gene analyses (Haseloff, 1999;Moriau et al, 1999) and DNA microarray technology (Schena et al, 1995) will be employed on a large scale to study gene expression as a function of space, time, and environmental conditions. In the different subfamilies, knockout mutants for all members will be isolated and multiple knockouts will be generated by crossing these lines (Young et al, 2001).…”

Plant Plasma Membrane H+-ATPase in Adaptation of Plants to Abiotic Stresses

“…It has been shown that various genes are expressed in the same organ. Moreover, even within the same cell type at the same developmental stage, at least two H + -ATPase genes are expressed (Harms et al, 1994;Hentzen et al, 1996;Moriau et al, 1999). In N. plumbaginifolia two different plasma membrane H + -ATPase genes, PMA2 and PMA4, are expressed in guard cells (Moriau et al, 1999).…”