Functional Analysis Of OsLPA4 That Regulates Rice Tiller Angle

Tiller angle is one of the important agronomic traits of rice(Oryza sativa L.),which is closely related to yield.Therefore,the exploration of new tiller angle regulatory genes is of great significance for elucidating the mechanism of rice tiller angle.In this study,we performed explorative study of a rice tiller angle regulatory gene Loose plant architecture 4(OsLPA4).The main results are as follows:(1)OsLPA4 encoding an acidic protein with 353 amino acids,which is an unstable protein,without transmembrane domain.The expression pattern of OsLPA4 was observed by real-time PCR and RUBY reporter system,the result showed that OsLPA4 was expressed in all tissues,with the most abundant expression occurring in the leaves and leaf sheaths.Subcellular localization results showed that OsLPA4 was localized mainly in the cytoplasm.(2)lpa4 mutants showed the phenotype with loose plant architecture,decreased plant height and gravity response.Overexpressing OsLPA4 transgenic plants showed enhanced gravity response.We investigated the auxin content by analyzing GUS activity levels in the wild type zhonghua 11(ZH11)and lpa4 using the auxin reporter DR5:GUS.The results showed that the GUS activity levels at the shoot of the lpa4 were markedly less intense than that of ZH11,indicated that the auxin in the shoot of lpa4 decreased compared with in the ZH11.We examined the expression of the auxinresponsive marker gene Os IAA20 in the shoot bases of ZH11 and lpa4 seedlings upon gravistimulation.The results showed that the ratio of expression of Os IAA20 of the lower side(LS)/upper side(US)in lpa4 was lower than that of ZH11.This suggested that OsLPA4 affected lateral auxin transport(LAT)at the base of rice stems.(3)RNA-seq results showed that there were 254 different expression genes(DEGs)between lpa4 and ZH11 under gravity stimulation(192 genes were upregulated and 62 genes were downregulated).The GO and KEGG pathway analysis the DEGs were clustered and mainly focused on terpenoids synthesis and metabolism.The expression of starch synthesis,auxin synthesis and signal transduction related genes to changed significantly,and genes related to cell wall relaxation were significantly downregulated.In conclusion,the OsLPA4 regulates the gravity response and tiller angle of rice by affecting auxin synthesis and lateral transport.