Abstract
BackgroundPlant receptor-like kinase (RLK/Pelle) family regulates growth and developmental processes and interaction with pathogens and symbionts.Platanaceae is one of the earliest branches of Eudicots temporally located before the split which gave rise to Rosids and Asterids. Thus investigations into the RLK family in Platanus can provide information on the evolution of this gene family in the land plants.Moreover RLKs are good candidates for finding genes that are able to confer resistance to Platanus pathogens.ResultsDegenerate oligonucleotide primers targeting the kinase domain of stress-related RLKs were used to isolate for the first time 111 RLK gene fragments in Platanus × acerifolia. Sequences were classified as candidates of the following subfamilies: CrRLK1L, LRR XII, WAK-like, and LRR X-BRI1 group. All the structural features typical of the RLK kinase domain were identified, including the non-RD motif which marks potential pathogen recognition receptors (PRRs). The LRR XII candidates, whose counterpart in Arabidopsis and rice comprises non-RD PRRs, were mostly non-RD kinases, suggesting a group of PRRs. Region-specific signatures of a relaxed purifying selection in the LRR XII candidates were also found, which is novel for plant RLK kinase domain and further supports the role of LRR XII candidates as PRRs. As we obtained CrRLK1L candidates using primers designed on Pto of tomato, we analysed the phylogenetic relationship between CrRLK1L and Pto-like of plant species. We thus classified all non-solanaceous Pto-like genes as CrRLK1L and highlighted for the first time the close phylogenetic vicinity between CrRLK1L and Pto group. The origins of Pto from CrRLK1L is proposed as an evolutionary mechanism.ConclusionsThe signatures of relaxed purifying selection highlight that a group of RLKs might have been involved in the expression of phenotypic plasticity and is thus a good candidate for investigations into pathogen resistance.Search of Pto-like genes in Platanus highlighted the close relationship between CrRLK1L and Pto group. It will be exciting to verify if sensu strictu Pto are present in taxonomic groups other than Solanaceae, in order to further clarify the evolutionary link with CrRLK1L.We obtained a first valuable resource useful for an in-depth study on stress perception systems.Electronic supplementary materialThe online version of this article (doi:10.1186/1756-0500-7-884) contains supplementary material, which is available to authorized users.
Highlights
Plant receptor-like kinase (RLK/Pelle) family regulates growth and developmental processes and interaction with pathogens and symbionts
With regard to receptor-like kinases (RLKs)/Pelles, a striking difference between the land plant and non-plant eukaryote genomes is the size of this family, 329 genes have been identified in moss (Physcomitrella patens), 610 in Arabidopsis, 647 in tomato, 1192 in poplar (Populus trichocarpa), 1070 in rice, 1 and 4 in the animals Drosophila melanogaster and Homo sapiens respectively, and none have been identified in fungal organisms [5,6]
Non-RD kinases are present in the kinomes of a wide range of Eukaryotic organisms and a statistically significant and positive correlation was found between kinases that function in the innate immunity and the non-RD motif [81]. This finding, together with the fact that Arabidopsis and rice LRR XII contain pathogen recognition receptors (PRRs), suggests that we have identified a group of genes that is potentially involved in the perception of pathogens
Summary
Plant receptor-like kinase (RLK/Pelle) family regulates growth and developmental processes and interaction with pathogens and symbionts. The counterpart of RTKs and STRKs is represented by the family of receptor-like kinases (RLKs), which share the same domain composition [3]. It has been suggested that one of the evolutionary reasons for the gene family’s expansion derives from the need to cope, as sessile organisms, with an ever-changing environment, including a multitude of mutating pathogenic and would be-pathogenic microbes [4,5,7] This would account for the variety of RLK/ Pelle types - 53 subfamilies categorized in Arabidopsis - for the genetic redundancy present in part of the subfamilies, and for the up-regulation of hundreds of RLK/Pelle members under biotic stress [3,4,5,7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
