Abstract
Water stress has a major influence on plant growth, development, and productivity. However, the cross-talk networks involved in drought tolerance are not well understood. Arabidopsis PCaP2 is a plasma membrane-associated Ca2+-binding protein. In this study, we employ qRT-PCR and β-glucuronidase (GUS) histochemical staining to demonstrate that PCaP2 expression was strongly induced in roots, cotyledons, true leaves, lateral roots, and whole plants under water deficit conditions. Compared with the wild type (WT) plants, PCaP2-overexpressing (PCaP2-OE) plants displayed enhanced water deficit tolerance in terms of seed germination, seedling growth, and plant survival status. On the contrary, PCaP2 mutation and reduction via PCaP2-RNAi rendered plants more sensitive to water deficit. Furthermore, PCaP2-RNAi and pcap2 seedlings showed shorter root hairs and lower relative water content compared to WT under normal conditions and these phenotypes were exacerbated under water deficit. Additionally, the expression of PCaP2 was strongly induced by exogenous abscisic acid (ABA) and salicylic acid (SA) treatments. PCaP2-OE plants showed insensitive to exogenous ABA and SA treatments, in contrast to the susceptible phenotypes of pcap2 and PCaP2-RNAi. It is well-known that SNF1-related kinase 2s (SnRK2s) and pathogenesis-related (PRs) are major factors that influence plant drought tolerance by ABA- and SA-mediated pathways, respectively. Interestingly, PCaP2 positively regulated the expression of drought-inducible genes (RD29A, KIN1, and KIN2), ABA-mediated drought responsive genes (SnRK2.2, -2.3, -2.6, ABF1, -2, -3, -4), and SA-mediated drought responsive genes (PR1, -2, -5) under water deficit, ABA, or SA treatments. Taken together, our results showed that PCaP2 plays an important and positive role in Arabidopsis water deficit tolerance by involving in response to both ABA and SA signals and regulating root hair growth. This study provides novel insights into the underlying cross-talk mechanisms of plants in response to water deficit stress.
Highlights
Water deficit is one of the most acute abiotic stresses affecting plant growth and the economic yield of crop plants
To fully understand the expression pattern of PCaP2 under water deficit stress, we examined the expression of PCaP2 in more details by quantitative real-time PCR and β-glucuronidase (GUS) staining
GUS staining showed that the promoter activity of PCaP2 was significantly increased after water deficit treatments for 6 h which was consistent with the results of quantitative real-time PCR (qRT-PCR) (Figure 1B) and PCaP2 expression was induced in primary roots and lateral roots, cotyledons, true leaves, and the whole seedlings after water deficit treatments (Figures 1B–D)
Summary
Water deficit is one of the most acute abiotic stresses affecting plant growth and the economic yield of crop plants It leads to alterations in various cellular processes in plants, for example, gene expression, photosynthesis, protein synthesis, carbon partitioning, lipid metabolism, and osmotic homeostasis (Hua et al, 2012; Jarzyniak and Jasinski, 2014; Fleta-Soriano and Munné-Bosch, 2016). This could be because SnRK2.6/ OST1 are important for stomatal movements, as they phosphorylate anion (SLAC1) and cation (KAT1) channels, Abbreviations: ABA, abscisic acid; ABF, abscisic acid responsive elementbinding factor; ABI, abscisic acid insensitive; AREBs/ABFs, ABRE-binding proteins/factors; Ca2+, calcium ion; CaM, calmodulin; CCD, charge-coupled device; CPK, calcium-dependent protein kinase; Di19, drought-induced 19; GA, gibberellin; GR, glutathione reductase; GST, glutathione s-transferase; GUS, β-glucuronidase; IAA, indole-3-acetic acid; JA, jasmonic acid; KIN, kinase; MDHAR, Monodehydroascorbate reductase; MAP18/PCaP2, microtubuleassociated protein18/plasma membrane-associated Ca2+-binding protein-2; MT, microtubule; MS, Murashige Skoog; NO, nitric oxide; OST1, open stomata; PA, phosphatidic acid; PCaP2-OE, PCaP2 overexpression; PCaP2-RNAi, PCaP2 RNA interference; PEG, polyethylene glycol; PR, pathogenesis-related; PtdInsPs, phosphatidylinositol phosphates; qRT-PCR, quantitative real-time PCR; RD29A, responsive to desiccation 29A; RT-PCR, reverse transcriptase-mediated PCR; SA, salicylic acid; S. lycopersicum, Solanum lycopersicum; SNF, sucrose nonfermenting; SnRK2, SNF1-related protein kinase 2; WT, wild type; Z. mays, Zea mays; RGGA, Arginine Glycine Glycine (RGG) box-containing RNA-binding protein; Di19, drought-induced protein
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