Study On Mechanism Of Spindling-control Of Cucumber In Seedlings By LEDs Light Quality

Cucumber(Cucumis sativus L.)is one of the most important vegetable largest vegetable in the world.Under high temperature and humidity,light deficiency,the cucumber seedling express the tendency of spindling,and cucumber seedling quality decline is induced,and vegetative and reproduction growth will be affected which might finally lead to significant losses in yield and quality.The effect of light quality on cucumber seedling hypocotyl elongation and related regulatory genes expression such as light receptors,light regulator,and the key enzyme plant hormone biosynthesis were studied under weak light.The results showed that:1?The rapid elongation of hypocotyls of cucumber seedlings was found between cotyledon and one leaf stage,and the hypocotyls elongated rapidly at about 1 ~3d by after cotyledon expansion.Compared with the control,hypocotyl elongation of cucumber seedlings were significantly inhibited under 2R1B?1R1B and 1R2 B treatments.2?Compared with the control treatment,the elongation growth of hypocotyls of cucumber seedlings was significantly inhibited by red and blue supplement,and the inhibition was positively correlated with the ratio of red light and blue light.The biomass and seedling index increased significantly under 2R1 B treatments.3.Compared with the control treatment,the expression of HY5 obviously increased under red and blue supplement.The expression levels of COP1 under 1R2 B treatments was higher than those of the other LED treatments.The PIF4 expression levels of under 2R1 B treatment was higher than that 1R2 B treatment,which indicated that the increase of blue light intensity could inhibit the activity of PIF4.Compared with the control treatment,the expression levels of GA20ox1?GA3ox1?GA20ox2 increased under LED treatments.The expression levels of GA3ox1 significantly reduced in the 2R1 B treatment compared with 1R1 B and 1R2 B treatments.Compared with the control treatment,the expression levels of IAA3?YUC8 enhanced under LED treatments.The expression levels of IAA3 under the 2R1 B treatment was significantly lower than 1R1 B and 1R2 B.The expression levels of YUC8 in 1R2 B treatment were significantly higher than those of other treatments.The expression levels of BRI1 and DET2 enhanced by higher of red light supplement.4.In the plant by VIGS silencing CsPIF4 gene,the expression of CmPIF4 and the key genes gibberellin synthesis(GA20ox1,GA20ox2 and GA3ox1)significantly decreased.PIF4 might play an important role in the negative regulation of controlling Spindling in cucumber seedlings by different light quality.In conclusion,PIF4 might be involved in phytohormone biosynthesis or signal transduction pathway,which interacts with gibberellin,auxin and brassinolide to regulate the elongation of hypocotyls.The expression levels of GA3ox1?IAA3?BRI1 could be significantly promote by different light quality treatments.while the content of GA in plants increased,the biosynthesis of DELLA protein was inhibited,therefore,promoting GA signaling transduction.In addition,DELLA could interact with ARF6,BRI1 and PIF4 and inhibited the transcriptional activity by blocking binding to target gene promoter to finally control spindling of cucumber seedlings.