Receptor-Like Kinases MDKs Regulate Meristem Development In Arabidopsis Thaliana

Plant receptor-like kinases (RLKs) are the homologous proteins of animal protein kinases, locating on cell membrane to perceive external environmental stimuli and playing important roles in cellular signal transduction and development. There are more than 600 RLKs in Arabidopsis, forming the largest protein superfamily. Among them, leucine-rich repeat receptor-like kinases (LRR-RLKs) belong to the largest gene family and were divided into 13 subfamilies based on the homology relationship of intracellular kinase domain. Members of a subfamily were revealed to regulate meristem development in Arabidopsis and were then named as Meristem Development Receptor-Like Kinases (MDKs). The central zone of meristem contains a population of stem cells that can self-renew with active metabolism and low level of differentiation. All the tissues and organs of Arabidopsis are derived from the proliferation and differentiation of stem cells. The shoot apical meristem converts subsequently into the inflorescence meristem when plants transit from vegetative growth to reproductive growth, while the axillary meristems can be formed in the leaf axils. In this study, scanning electron microscopy, gene expression pattern analysis and molecular biology were employed to analyze MDKs regulating meristem development in Arabidopsis. The mdk2 mdk3 mdk4+/- triple mutant plants appeared defects in meristem development, resulting in dwarf plant and slow development. The axillary branches in rosette leaf increase in stage of reproductive growth and the main stem is not obvious, suggesting that plant apical dominance may be affected. Expression pattern analyses revealed that MDKs express in meristems. Data of the complementary experiments proved that mutant phenotypes were caused indeed by loss-of-function of MDKs. Our data also showed that the phenotype might relate to cytokinin, auxin and some transcription factors. But the signaling pathway mediated by MDKs to regulate meristem development is unclear and further studies will be needed in the future.