Function Analysis Of Receptor-like Kinase RLK80 In Arabidopsis Thaliana

Receptor-protein kinase(RLK) is a kind of important plant protein kinase, which is located in a cell membrane.Plants can’t move, so plant genomes evolved out hundreds of receptor-protein kinase(RLK) members to response and adapt to diverse environments. They can perceive and receive extracellular signals, and transfer them inside cells. Up to now, tens of RLK had their functions identified, which play important roles in the plant growth and development. Further study on the biological functions of other members of RLK is of great significance.RLK80(AT5G67280) is one of the RLKs, belonging to leucine-rich receptor protein kinase LRR Ⅲ-RLK subfamily, which encodes a transmember protein containing 751 amino acids. Its biological function has not been reported. The function of RLK80 was analyzed preliminarily, from the mutant phenotype, tissue expression pattern, protein subcellular localization, to the protein interactions. The main results are shown below:1、First, in terms of plant growth and development, rlk80-1 mutant organs get enlarged. Compared with the wild type control(Col.0), many organs in rlk80-1 get enlarged including seeds, leaves, flowers, pollens and pods, especially the seeds. The mutant seed development in different periods of transparent observed, seeds increased in the early stage of globular embryo, and the increasing amplitude getting more obvious in heart-shaped embryo, torpedo embryo stage. The weight of one-hundred rlk80-1 seeds is 2.85 mg, while the control is 1.72 mg. Compared with wild type control, rlk80-1 seeds increased about 65% of the weight. The rlk80-1 mutant displayed empty seatsin the siliques, less pollens in the taptum, though morphological structure of the pollens is basically normal.2、 RLK80 is localized to the plasmembrane. A RLK80-GFP cassette was constructed and transformed into Arabidopsis plants or arabidopsis protoplasts. The transgenic plants root tip cells were observed by laser confocal microscopy, the plasmembrane in the root tip cells emitted fluorescence, suggesting RLK80 is localized to the plasmembrane. To further confirm this localization, 35S::RLK80-GFP plasmids were transformed into arabidopsis protoplast, and GFP signals were detected with a laser confocal microscope. Clear green fluorescence can be observed in protoplast membrane. Two consistent results indicate RLK80 is a plasma membrane protein.3、RLK80 is expressed with wide range. Semi-quantitative results showed that RLK80 expressed in root, leaf, flower, silique, but less expression in the stem, and the content changes in the organs displayed from high to low:flower > leaf > root > silique. The transgenic plants of GUS reportor gene driven by RLK80 promoter were constructed in arabidopsis thaliana. GUS signals were stained in seedlings, lateral root, stigma, sepals, anther, porosity and ovule, of which the female gametophytes have the highest amount of expression.4、Four RLK80-interactingprotein candidates were screened by Y2H(Yeast Two Hybrid).They are BIM1, GAI, IDD14, CPHSC70-1, of which the interaction between BIM1 and RLK80 was confirmed in the yeast two hybrid systems.From the data above, we conclude that RLK80 received the extracelluar signal by its N-terminal domain and transduct the signal inside the cells by its C-terminal domain interacting with BIM1, probably by phosphorylation, activating some pathway to regulate embryo development and seed size.