Evolutionary History and Stress Regulation of Plant Receptor-Like Kinase/Pelle Genes    

Abstract

Receptor-Like Kinase (RLK)/Pelle genes play roles ranging from growth regulation to defense response, and the dramatic expansion of this family has been postulated to be crucial for plant-specific adaptations. Despite this, little is known about the history of or the factors that contributed to the dramatic expansion of this gene family. In this study, we show that expansion coincided with the establishment of land plants and that RLK/Pelle subfamilies were established early in land plant evolution. The RLK/Pelle family expanded at a significantly higher rate than other kinases, due in large part to expansion of a few subfamilies by tandem duplication. Interestingly, these subfamilies tend to have members with known roles in defense response, suggesting that their rapid expansion was likely a consequence of adaptation to fast-evolving pathogens. Arabidopsis (Arabidopsis thaliana) expression data support the importance of RLK/Pelles in biotic stress response. We found that hundreds of RLK/Pelles are up-regulated by biotic stress. Furthermore, stress responsiveness is correlated with the degree of tandem duplication in RLK/Pelle subfamilies. Our findings suggest a link between stress response and tandem duplication and provide an explanation for why a large proportion of the RLK/Pelle gene family is found in tandem repeats. In addition, our findings provide a useful framework for potentially predicting RLK/Pelle stress functions based on knowledge of expansion pattern and duplication mechanism. Finally, we propose that the detection of highly variable molecular patterns associated with specific pathogens/parasites is the main reason for the up-regulation of hundreds of RLK/Pelles under biotic stress.

Duplicate and Conquer: Multiple Homologs ofPHOSPHORUS-STARVATION TOLERANCE1Enhance Phosphorus Acquisition and Sorghum Performance on Low-Phosphorus Soils

“…However, SNPs within Sb03g006765 at position 7 Mb are not in LD with those within the SbPSTOL1 cluster at position 60 Mb, suggesting that multiple SbPSTOL1 homologs enhance sorghum performance under low-P conditions, likely by the same overall physiological mechanism based on root morphology modulation. Lehti-Shiu et al (2009) found that RLKs present in tandem repeats were more likely than nontandem RLKs to be up-regulated by biotic stress factors and UV-B light in Arabidopsis, suggesting that the SbPSTOL1 homologs close together at position 60 Mb on chromosome 3 may constitute a functional module controlled by common regulatory elements. If so, similar to the case for maize aluminum tolerance (Maron et al, 2013), tandem duplication events may provide an additional level of regulation, leading to enhanced gene expression and increased P acquisition controlled by PSTOL1 homologs in sorghum.…”

“…Although RLKs have been found to be important regulators of root hair growth in Arabidopsis under low-P conditions (Lan et al, 2013), their role seems to be much more general, as they also function in defense and stress responses, including drought, salinity, and cold (Lehti-Shiu et al, 2009;Ye et al, 2009;Das and Pandey, 2010;Marshall et al, 2012;Schulz et al, 2013;Vivek et al, 2013), possibly acting as hubs in stress signaling and development (Das and Pandey, 2010;Asano et al, 2012;Schulz et al, 2013). Several RLKs such as CRPK1 have been shown to play key roles in abiotic stress tolerance, positively or negatively regulating stress tolerance by modulating abscisic acid signaling and reducing the accumulation of reactive oxygen species (Lan et al, 2013).…”

“…The availability of complete sequences for several plant genomes now provides for a much more complete framework where functional variants can be identified via comparative genomics, even in potentially complex situations arising from ancient gene duplication events. This is likely the case of RLKs in plants ( Lehti-Shiu et al, 2009), a protein class to which PSTOL1 belongs. In view of that, based on the isolation of OsPSTOL1 in rice, we undertook a cross-species effort to identify homologs in the sorghum genome that are functional with regard to enhancing agronomic performance under low-P conditions, a common constraint for sustainable crop yield worldwide (Ismail et al, 2007).…”

“…RLKs constitute the largest family of receptors in plants, and the diverse structures in the receptor domains suggest that there are likely to be several biological functions for these proteins (Lehti-Shiu et al, 2009;Tör et al, 2009). Although RLKs have been found to be important regulators of root hair growth in Arabidopsis under low-P conditions (Lan et al, 2013), their role seems to be much more general, as they also function in defense and stress responses, including drought, salinity, and cold (Lehti-Shiu et al, 2009;Ye et al, 2009;Das and Pandey, 2010;Marshall et al, 2012;Schulz et al, 2013;Vivek et al, 2013), possibly acting as hubs in stress signaling and development (Das and Pandey, 2010;Asano et al, 2012;Schulz et al, 2013).…”

A Key Role for Apoplastic H2O2 in Norway Spruce Phenolic Metabolism

“…8D). CRK expression has been shown to be modulated in response to ROS-and cellular redox state-related stresses (Lehti-Shiu et al, 2009;Wrzaczek et al, 2010;Bourdais et al, 2015). Moreover, CRKs are thought to be involved in cellular redox and apoplastic ROS sensing by the presence of conserved Cys residues in their apoplastic domain.…”