A Group Of Receptor-like Cytoplasmic Kinases Regulate Root Growth And Seed Coat Development In Arabidopsis Thaliana

Receptor-like cytoplasmic kinases(RLCKs)are a group of receptor-like kinases without transmembrane domain and extracellular domain.Usually,RLCKs interact with LRR-RLKs and form a receptor complex.By modulating the phosphorylation status of the intracellular kinase domain,the exogenous signal is transmitted to the downstream components.RLCKs belong to a large family of receptor kinases.To data,more than 610 RLKs have been identified in Arabidopsis thaliana,including 147 RLCKs.Some studies showed that RLCKs play critical roles in plant growth,development and stress adaptations.In this study,660 individual transgenic plants,generated by mixing cloned RLCKs overexpression transformation vectors,have been screened and seven of them showed a shortened primary root phenotype.After analyzing the expression patterns of these seven genes,RLCK643 was chosen to explore its function.RLCK643 belongs to RLCK ? subfamily.T-DNA insertion mutants rlck643,rlck643 rlck642 and rlck643 rlck642 rlck639 all showed elongated primary roots.The root thigmotropism of the double mutants is more severe than that of wild-type seedlings.Furthermore,we found rlck643 rlck642 rlck639 is hypersensitive to three small peptides in CLEs family.During the phenotypic analysis,we found the seed coat of the triple mutant seeds is abnormally developed.The mucilage cubage of rlck643 rlck642 rlck640 is significantly reduced than that of wild-type seeds.Isoxaben,a cellulose synthesis inhibitor,shows stronger root growth inhibition in rlck643 rlck642 rlck640.Meanwhile,cellulose synthases were also found to interact with RLCK642 and RLCK639 by a mass spectrometry.During exploring the molecular mechanism of mucilage release,SERKs,a group of well studies receptor kinases,were found to affect mucilage release of seeds.Yeast two-hybrid assay showed that SERK1,SERK2 and SERK3 interact with RLCK643 and its homologs.In summary,RLCK643 and its homologous genes were found to be involved in root growth and development.In addition,RLCK643 and its homologous proteins can interact with SERKs,affecting cellulose synthesis by regulating cellulose synthase that is essential for seed coat development and the release of mucilage in seeds.To data,it has not been reported that RLCKs are involved in seed coat development and mucilage release.This study may reveal a new regulatory mechanism of seed coat development and mucilage release,providing insights for relevant studies in the future.