Abstract
BackgroundIn plants, calcium-dependent protein kinases (CDPKs) are involved in tolerance to abiotic stresses and in plant seed development. However, the functions of only a few rice CDPKs have been clarified. At present, it is unclear whether CDPKs also play a role in regulating spikelet fertility.ResultsWe cloned and characterized the rice CDPK gene, OsCPK9. OsCPK9 transcription was induced by abscisic acid (ABA), PEG6000, and NaCl treatments. The results of OsCPK9 overexpression (OsCPK9-OX) and OsCPK9 RNA interference (OsCPK9-RNAi) analyses revealed that OsCPK9 plays a positive role in drought stress tolerance and spikelet fertility. Physiological analyses revealed that OsCPK9 improves drought stress tolerance by enhancing stomatal closure and by improving the osmotic adjustment ability of the plant. It also improves pollen viability, thereby increasing spikelet fertility. In OsCPK9-OX plants, shoot and root elongation showed enhanced sensitivity to ABA, compared with that of wild-type. Overexpression and RNA interference of OsCPK9 affected the transcript levels of ABA- and stress-responsive genes.ConclusionsOur results demonstrated that OsCPK9 is a positive regulator of abiotic stress tolerance, spikelet fertility, and ABA sensitivity.
Highlights
In plants, calcium-dependent protein kinases (CDPKs) are involved in tolerance to abiotic stresses and in plant seed development
After abscisic acid (ABA) treatment, the expression of OsCPK9 increased at 1 h and reached the highest level at 3 h followed by a decrease (Figure 1B)
OsCPK9 plays a positive role in drought, osmotic, and dehydration stress responses OsCPK9 belongs to the group III-b CDPK family [22]
Summary
Calcium-dependent protein kinases (CDPKs) are involved in tolerance to abiotic stresses and in plant seed development. CPK6 activates the slow anion channel (SLAC1) and CPK3 activates SLAC1 as well as its guard cell homolog SLAH3 These activations are calcium-dependent and are controlled by the ABA signaling component phosphatase ABI1 [14,15]. CPK32 phosphorylates the ABA-responsive transcription factor ABF4 in vitro, and CPK32-overexpressing plants displayed increased sensitivity to ABA during seeds germination as a result of up-regulated expressions of genes controlled by ABF4 [16]. CPK10, through its interaction with heat shock protein 1 (HSP1), plays a role in ABA- and Ca2+-mediated regulation of stomatal movement [17]. Together, these studies have shown that Arabidopsis CPK family members can positively regulate abiotic stress tolerance and ABA signaling
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