Seed germination and innate immunity both have significant effects on plant life spans because they control the plant's entry into the ecosystem and provide defenses against various external stresses, respectively. Much ecological evidence has shown that seeds with high vigor are generally more tolerant of various environmental stimuli in the field than those with low vigor. However, there is little genetic evidence linking germination and immunity in plants. Here, we show that the rice lectin receptor-like kinase OslecRK contributes to both seed germination and plant innate immunity. We demonstrate that knocking down the OslecRK gene depresses the expression of α–amylase genes, reducing seed viability and thereby decreasing the rate of seed germination. Moreover, it also inhibits the expression of defense genes, and so reduces the resistance of rice plants to fungal and bacterial pathogens as well as herbivorous insects. Yeast two-hybrid and co-immunoprecipitation experiments revealed that OslecRK interacts with an actin-depolymerizing factor (ADF) in vivo via its kinase domain. Moreover, the rice adf mutant exhibited a reduced seed germination rate due to the suppression of α–amylase gene expression. This mutant also exhibited depressed immune responses and reduced resistance to biotic stresses. Our results thus provide direct genetic evidence for a common physiological pathway connecting germination and immunity in plants. They also partially explain the common observation that high-vigor seeds often perform well in the field. The dual effects of OslecRK may be indicative of progressive adaptive evolution in rice.
種子萌發(fā)和免疫反應(yīng)在植物生活史中均發(fā)揮重要作用，因?yàn)樗鼈兎謩e控制植物進(jìn)入生態(tài)系統(tǒng)以及提供防衛(wèi)反應(yīng)抵御各種外部脅迫。許多生態(tài)學(xué)證據(jù)表明，在大田生長環(huán)境下，高活力的種子對各種環(huán)境刺激的耐受性通常要高于低活力種子。但是，幾乎沒有證據(jù)將種子萌發(fā)和植物免疫聯(lián)系起來。本文我們發(fā)現(xiàn)水稻凝集素類受體激酶OslecRK在種子萌發(fā)和植物先天免疫反應(yīng)過程中均發(fā)揮作用。我們發(fā)現(xiàn)敲減OslecRK基因會抑制α-淀粉酶基因的表達(dá)，降低種子活力，進(jìn)而使種子萌發(fā)率降低。此外，敲減OslecRK還會抑制防衛(wèi)反應(yīng)基因的表達(dá)，進(jìn)而降低水稻對真菌和細(xì)菌病原菌以及害蟲的抗性。酵母雙雜和免疫共沉淀實(shí)驗(yàn)表明，在體內(nèi)OslecRK通過它的激酶結(jié)構(gòu)域與肌動蛋白解聚因子（ADF）互作。此外，水稻adf突變體中，由于α-淀粉酶基因的表達(dá)被抑制，導(dǎo)致種子萌發(fā)率降低。突變體還會表現(xiàn)出免疫反應(yīng)被抑制以及對非生物脅迫抗性降低的表型。因而，我們的結(jié)果為解釋聯(lián)系植物種子萌發(fā)和免疫反應(yīng)的常規(guī)生理通路提供了直接的遺傳證據(jù)。它們還部分解釋了大田中高活力種子通常長的比較好這一常規(guī)現(xiàn)象。OslecRK的雙效作用可能是水稻逐步適應(yīng)性進(jìn)化的特征。