A RLCK gene, GUDK(GROWTH UNDER DROUGHT KINASE) is a drought inducible receptor-like cytoplasmic kinase (RLCK).
- GUDK is important for grain yield production not only under drought but also under well-watered conditions. Loss-of-function of GUDK increases sensitivity of rice seedlings to abiotic stress (salinity, osmotic stress and ABA treatment). GUDK is a Mg 2+ dependent, dual-specificity, autophosphorylating protein kinase.
A phosphorylation target of GUDK
OsAP37 is a phosphorylation target of GUDK:
- The high induction under drought of GUDK in flag leaf and reduced photosynthesis in the mutant lines suggests that GUDK regulates photosynthesis and carbon metabolism genes by phosphorylating OsAP37 and resulting in sustained yield. A working model of GUDK under early events of drought stress signaling and transcriptional activation of drought-regulated genes is shown in Figure 1.
- In response to drought, signals are transmitted to GUDK and via phosphorylation (P) to transcription factor OsAP37, which is activated and in turn trancriptionally activates genes involved in photosynthetic carbon metabolism and drought tolerance(Figure 1).
- Phosphoproteome profiling of the mutant followed by in vitro assays identified the AP2/ERF transcription factor OsAP37 as a phosphorylation target of GUDK.
- In presence of reporters and OsAP37 or GUDK alone the luminescence was low. The luminescence increased by nearly 2-fold in presence of OsAP37 along with GUDK suggesting that GUDK function is essential for OsAP37 activation and in turn regulation of the down-stream targets.
Two independent T-DNA insertion mutant lines:
- Under drought stress, the mutant lines showed a significant 8% to 14% increase in spikelet sterility over wild-type plants. A significant reduction in spikelet sterility was also observed under well-watered treatments of mutant lines compared with wild-type plants.
- Grain yield of mutant lines was reduced under well-watered as well as drought stress conditions.
- Under well-watered conditions, there was 2.8 to 3.1 g (25%–28%) less yield in mutant lines compared with the wild type.
- Under drought, the yield reduction in mutant lines was 2.1 to 2.8 g compared with wild-type plants.
- Loss-of-function gudk mutant lines exhibit sensitivity to salinity, osmotic stress and ABA treatment at the seedling stage, and reduction in photosynthesis and plant biomass under controlled drought stress at the vegetative stage. The gudk mutants interestingly showed significant reduction in grain yield, both under normal well watered conditions and under drought stress at the reproductive stage.
- There was 1.1 to 1.8 g reduction in biomass of mutant lines under drought stress condition when compared to WT plants supporting the role of GUDK in drought tolerance for growth of rice plants at the vegetative stage.
GUDK with gene size of 6080 nucleotides and deduced protein length of 425 amino acids, showed 64% identity with an Arabidopsis uncharacterized protein kinase superfamily protein (At1g61590). The structural predictions using deduced amino acid sequence showed RLCK features with only an intracellular kinase domain and no transmembrane or extracellular domains.
- Receptor-like cytoplasmic kinases (RLCKs) in plants belong to the super family of receptor-like kinases (RLKs). These proteins show homology to RLKs in kinase domain but lack the transmembrane domain. Some of the functionally characterized RLCKs from plants have been shown to play roles in development and stress responses.
- Previously, 149 and 187 RLCK encoding genes were identified from Arabidopsis and rice, respectively. By using HMM-based domain structure and phylogenetic relationships, 379 OsRLCKs were identified from rice. OsRLCKs are distributed on all 12 chromosomes of rice and some members are located on duplicated chromosomal segments.
- Differential expression patterns observed for majority of OsRLCKs during development and stress suggest their involvement in diverse functions in rice. Majority of the stress-responsive OsRLCKs were also found to be localized within mapped regions of abiotic stress QTLs. Outcome of this study would help in selecting organ/development stage specific OsRLCK genes/targets for functional validation studies.
Labs working on this gene
- Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville, Arkansas 72701;
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061.
- These authors contributed equally to this work.
- Ramegowda V, Basu S, Krishnan A, et al. The rice receptor-like cytoplasmic kinase GUDK is required for drought tolerance, and grain yield under normal and drought stress conditions[J]. Plant Physiology, 2014: pp. 114.248203.
- Vij S, Giri J, Dansana P K, et al. The receptor-like cytoplasmic kinase (OsRLCK) gene family in rice: organization, phylogenetic relationship, and expression during development and stress[J]. Molecular plant, 2008, 1(5): 732-750.