LRR50參與在保衛細胞的移動且其大量表現株會增強植物的防禦反應

Abstract

多亮胺酸重複類受體激酶(LRR-RLKs)是屬於類受體激酶家族的一員，而這個家族在植物對抗生物逆境及非生物逆境的過程中扮演很重要的角色。而本篇文章中我們所要探討的基因:阿拉伯芥類Malectin蛋白/類多亮胺酸重複類受體激酶LRR50是一個被認為參與在阿拉伯芥對抗微生物的基因。在先前的研究中，LRR50被發現會受到細菌性斑點病病原菌Pseudomonas syringae pv tomato (Pst) DC3000的誘導而提高其基因表現量。然而，在突變掉LRR50的突變株中則會使阿拉伯界對於Pst. DC3000的感染變得較為感病。突變掉LRR50後亦會使得阿拉伯芥對於病原菌變得更加感病，而這些突變後產生缺陷的徵狀恰恰好與阿拉伯芥某些PAMP誘發免疫反應(PTI)相符。而其中比較值得注意的是在LRR50突變株中，受到Pst DC3000誘導所聚集的葡萄肽聚醣(callose)與野生型植株相比明顯下降，且氣孔的關閉也變得較不明顯。值得一提的是在經過離層酸(ABA)處理之後LRR50突變株的氣孔並不會受到ABA誘導而關閉，這個現象指出LRR50可能在ABA所誘導的氣孔關閉路徑中扮演一個相當重要的角色。為了更進一步的研究LRR50的功能，我們建立了此基因的回復株以及大量表現株，並觀察其受到Pst DC3000感染之後感染程度的差異。從結果可以得知：回復株的感染程度可以回復到與野生型相仿的程度，而LRR50的大量表現株則變得更加抗病。這些結果都告訴我們LRR50會參與在PAMP誘發免疫反應(PTI)中，且參與在ABA所調控的氣孔關閉路徑中。

Leucine-rich repeat receptor like kinases (LRR-RLKs) belong to a RLK family that plays a role in both biotic and abiotic stress resistance. The gene Leucine-rich repeat receptor like kinase 50 (LRR50) is thought to participate in Arabidopsis thaliana defense to microbial pathogens. In a previous study, LRR50 was shown to be up-regulated during infection by virulent Pseudomonas syringae pv tomato (Pst) DC3000 bacteria. In addition, a lrr50 knock-out mutant demonstrated an enhanced susceptibility phenotype to Pst DC3000. The lrr50 mutant increased susceptibility phenotype was correlated with some defects in the pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) response. Notably, reduced callose depositions and weakened stomatal immunity were observed in lrr50 after Pst DC3000 inoculation. Stomata of the lrr50 mutant did not close in response to abscisic acid (ABA) treatment suggesting a role for LRR50 in the ABA-mediated stomatal closure. To further analyze the function of LRR50, complementary and overexpression lines were generated and inoculated with Pst DC3000. Complementary lines resistance levels to Pst DC3000 infection was back to wild type levels, while LRR50 overexpression lines were more resistant to virulent bacteria. Enhanced resistance was correlated with a reinforced PTI response. Our data reveal that LRR50 play a role in the PTI response, and in the ABA-mediated stomatal closer in Arabidopsis.