Abstract
In plant cells, vacuolar H+-ATPases (V-ATPases) are responsible for deacidification of the cytosol and energisation of the secondary transport processes across the tonoplast. A number of V-ATPase subunit genes have been demonstrated to be involved in the regulation of the plant response to water deficit. However, there are no reports on the role of V-ATPase subunit A (VHA-A) in dehydration tolerance of cotton. In this study, cotton GhVHA-A gene was functionally characterized, especially with regard to its role in dehydration stress tolerance. Expression analysis showed that GhVHA-A was differentially expressed in various cotton organs and was induced by dehydration, low temperature, high salinity, and abscisic acid treatment in leaves. We also report that GhVHA-A improve dehydration tolerance in transgenic tobacco and cotton. Virus-induced gene silencing of GhVHA-A decreased the tolerance of cotton plantlets to dehydration stress. Silencing GhVHA-A decreased chlorophyll content and antioxidant enzyme activities and increased malondialdehyde (MDA) content in cotton under dehydration stress. However, transgenic tobacco expressing GhVHA-A exhibited enhanced dehydration resistance, resulting in reduced leaf water loss, higher average root length, and lower MDA levels under dehydration stress. Meanwhile, overexpression of GhVHA-A in tobacco conferred water deficit tolerance by enhancing osmotic adjustment (proline) and the activities of the antioxidant enzymes superoxide dismutase and peroxidase, thereby enhancing reactive oxygen species detoxification. These results suggest that GhVHA-A plays an important role in conferring resistance to dehydration stress. Our results have identified GhVHA-A as a candidate gene for improving dehydration tolerance in plants.
Highlights
One way to improve plant drought tolerance is to increase the activity of the H+ pump on the tonoplast, allowing more H+ to enter the vacuole, producing a higher proton electrochemical gradient (H+) and increasing the solute concentration in plant cell vacuoles (Osmotic pressure regulation) and vacuolar osmotic pressure
The chlorophyll content was 18.132 mg g−1, which decreased to 11.898 mg g−1 (34.4%) in the leaves of virus-induced gene silencing (VIGS) plants after 15 days of waterwithholding treatment. This rate of decline is higher than that of EM and WT plants (Figure 3D). These results clearly indicated that silencing of GhVHA-A could decrease the resistance of cotton under dehydration stress
GhVHA-A is differentially expressed in plants exposed to diverse abiotic stresses
Summary
One way to improve plant drought tolerance is to increase the activity of the H+ pump on the tonoplast, allowing more H+ to enter the vacuole, producing a higher proton electrochemical gradient (H+) and increasing the solute concentration in plant cell vacuoles (Osmotic pressure regulation) and vacuolar osmotic pressure. V-PPase is a unique proton pump that composed of a single polypeptide, as a dimer of 71–80 kDa subunits, and has only been identified in plants and some algae, bacteria, protozoa, and archaebacterial (Maeshima, 2000) At this time, the V-PPase has been well characterized, and the heterologous overexpression of analogous genes encoding vacuolar membrane-bound pyrophosphatase (H+ PPase or H+ pump) from rice, tobacco, cotton and maize enhances salt and drought tolerance (Gao et al, 2006; Zhao et al, 2006; Li et al, 2008; Lv et al, 2008). Subunit A contains a highly conserved cysteine residue that may be involved in the regulation of holoenzyme, which is located in the enzyme catalytic center (Forgac, 1989)
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