| Potato plays a very important role in food security in China even the world.Meanwhile,late blight caused by Phytophthora infestans is the most destructive disease in damaging potato.Unfortunately,the control of the disease heavily rely on chemical spraying,resulting in huge resources consumption and environmental pollution.Therefore,developing environment-friendly and efficient preventive ways to prevent it have always been concerned and expected.By the way,light is not only a source of energy,but also an important signal for plants.In addition to chloroplasts,plants also utilize various photoreceptors located in cytoplasm and nucleus to sense and transduce light signals,adjusting its morphological and physiological responses to adapt to external changes.Previous studies have shown that light can regulate plant growth and development as well as immune defense processes.Moreover,our laboratory previously found that potato blue light photoreceptors StPHOT1/2 can regulate the late blight resistance of N.benthamiana.Based on the concept of“disease triangle”,this study focuses on the effect of environmental factors light quantity and quality as well as the light photoreceptors on the late blight resistance of N.benthamiana and S.tuberosum,aimming to explore a possible useful new way to prevent late blight by utilizing certain light and photoreceptors.In this study,we firstly investigate whether the blue/red light absorbed most by plants could affect the late blight resistance,then explore whether blue light photoreceptor cryptochromes,LOV/F-box/Kelch receptors and red and far-red light photoreceptor phytochromes involve in plant resistance regulation.The main findings are as follows:1.Compared with the white light(NWL,79.292μmol/m~2/s)control,the mycelium growth,sporangium yield and inoculum pathogenicity of P.infestans cultured on the medium plates treated with white supplemented with blue light(WBL,122.603μmol/m~2/s),white supplemented with red light(WRL,63.626μmol/m~2/s)significantly decrease,indicating that blue light and red light suppress the growth and pathogenicity of P.infestans.2.After pre-treated with white supplemented with red light(WRL)for five days,N.benthamiana was inoculated with P.infestans,the result shows that there are no significant differences in its lesion diameter,P.infestans biomass and the expression level of the PTI(Pattern Triggered Immunity)marker genes Nb WRKY7,Nb WRKY8 and Nb ACRE31 compared with the control,indicating that the red light does not affect the resistance of N.benthamiana.Instead,the expression level of these PTI marker genes decline in the inoculated N.benthamiana plants pre-treated with white supplemented with blue light(WBL),suggesting that the blue light represses the PTI of N.benthamiana.3.After P.infestans inoculation,N.benthamiana plants were treated with blue light(BL,11.155μmol/m~2/s),red light(RL,9.234μmol/m~2/s),weak white light(WL,10.141μmol/m~2/s)and normal intensity of white light(NWL,79.292μmol/m~2/s).The result shows that the lesion under blue light,red light and weak white light conditions dramatically magnify than that under normal white light(NWL).However,there is no difference in lesion diameter among the treated plants treated with blue light,red light and weak white light respectively.This indicates that the resistance of N.benthamiana is not only affected by light quality but also regulated by light intensity.4.The expression level of Nb CRY1a,Nb CRY1b,Nb CRY2,Nb PHYB and Nb PHYF in N.benthamiana plants treated with P.infestans culture filtrate(containing various P.infestans PAMPs)strongly induced to rise in a short time,showing these genes may involve in the PTI regulation.Transient overexpress of potato photoreceptor StCRY1a,StCRY1b,StFKF1,StPHYB and StPHYF on N.benthamiana markedly reduces the late blight.Moreover,the disease lesion diameter in N.benthamiana transgenic lines overexpressing StCRY2,StFKF1 markedly decrease than wild-type,indicating that the overexpression of StCRY1a,StCRY1b,StFKF1,StPHYB and StPHYF could positively regulate the late blight resistance of N.benthamiana.5.Compared with wild-type,potato transgenic lines silencing StCRY1(StCRY1a and StCRY1b),StCRY2 have no significant differences not only in disease area but sporangium yield after P.infestans inoculation.What’s more,potato transgenic lines silencing StPHYA,StPHYE have no effects on the late blight resistance while the potato transgenic lines silencing StPHYB,StPHYF obviously promote its lesion area than wild-type.This indicates that certain light photoreceptors may be involve in the late blight resistance regulation of potato and N.benthamiana,but different photoreceptors may be play complementary and redundant effects.This paper could enrich our understanding on how light and plant light photoreceptors regulate plant immunity,and contribute to the development and utilization of light and photoreceptors to regulate plant immune response. |
