Initial Functional Characterization Of Maize Phytochrome-Interacting Factors In Light Signaling And Photomorphogenesis

Increasing planting density has been an effective means of increasing maize yield per unit land area over the past few decades.However,high-density planting will cause a reduction in the ratio of red to far-red(R/FR)of incident light,which could trigger a series of shade avoidance syndrome(SAS),and negatively impact yield.The molecular mechanisms regulating SAS has been well established in Arabidopsis thaliana,but still remain poorly understood in maize.Here,we conducted an initial functional characterization of the maize Phytochrome-Interacting Factor(PIF)gene family in regulating light signaling and photomorphogenesis.The main results are as follows:1.The maize genome contains seven distinct PIF genes,which could be grouped into three subfamilies ZmPIF3s,ZmPIF4s,and ZmPIF5s.2.Similar to the Arabidopsis PIFs,all ZmPIFs protein are exclusively localized to the nucleus and most of them can form nuclear bodies upon light irradiation.3.All the ZmPIFs proteins could interact with ZmPHYB1 and ZmPHYB2.4.Overexpression of each ZmPIF member could partially or fully rescue the phenotype of the Arabidopsis pifq mutant,and some of them conferred enhanced shade avoidance syndrome in Arabidopsis.5.All of the ZmPIF proteins expressed in Arabidopsis are much more stable than their Arabidopsis counterparts upon exposure to red light.6.The Zmpif3s,Zmpif4s and Zmpif5s knockout mutants generated via CRISPR/Cas9 technology all showed severely suppressed mesocotyl elongation in dark-grown seedlings.7.ZmPIFs act as positive regulators in response to shade.Taken together,our results reveal both conserved and distinct molecular properties of ZmPIFs in regulating light signaling and photomorphogenesis in maize.Our results set up a foundation for future dissection of ZmPIFs in regulating plant architecture and SAS in maize,and might provide potential targets for genetic improvement of maize for adapting to high-density planting.