OsSPL10 controls trichome development by interacting with OsWOX3B at both transcription and protein levels in rice(Oryza sativa L.)

Plant trichomes are a specialized cellular tissue that functions in resistance to biotic and abiotic stresses.In rice,three transcription-factor genes:OsWOX3B,HL6,and OsSPL10,have been found to control trichome development.Although studies have shown interactions between the three genes,their full relationship in trichome development is unclear.We found that the expression levels of OsWOX3B and HL6 were both reduced in OsSPL10-knockout plants but increased in OsSPL10-overexpression plants,suggesting that OsSPL10 positively regulates their expression.Physical interaction between OsSPL10 and OsWOX3B was found both in vivo and in vitro and attenuated their abilities to bind to the promoter of HL6 to activate its transcription.This mechanism may regulate trichome length by adjusting the expression of HL6.A rice gene network regulating trichome development is proposed.

Receptor-like kinase OsCR4 controls leaf morphogenesis and embryogenesis by fixing the distribution of auxin in rice

Cell differentiation is a key event in organ development;it involves auxin gradient formation, cell signaling, and transcriptional regulation. Yet, how these processes are orchestrated during leaf morphogenesis is poorly understood. Here, we demonstrate an essential role for the receptor-like kinase Os CR4 in leaf development. oscr4 loss-of-function mutants displayed short shoots and roots, with tiny,crinkly, or even dead leaves. The delayed outgrowth of the first three leaves and seminal root in oscr4 was due to defects in plumule and radicle formation during embryogenesis. The deformed epidermal,mesophyll, and vascular tissues observed in oscr4 leaves arose at the postembryo stage;the corresponding expression pattern of pro Os CR4:GUS in embryos and young leaves suggests that Os CR4 functions in these tissues. Signals from the auxin reporter DR5 rev:VENUS were found to be altered in oscr4 embryos and disorganized in oscr4 leaves, in which indole-3-acetic acid accumulation was further revealed by immunofluorescence. Os WOX3 A, which is auxin responsive and related to leaf development,was activated extensively and ectopically in oscr4 leaves, partially accounting for the observed lack of cell differentiation. Our data suggest that Os CR4 plays a fundamental role in leaf morphogenesis and embryogenesis by fixing the distribution of auxin.

Rice SPL10 positively regulates trichome development through expression of HL6 and auxin-related genes

Trichomes function in plant defenses against biotic and abiotic stresses;examination of glabrous lines,which lack trichomes,has revealed key aspects of trichome development and function.Tests of allelism in 51 glabrous rice(Oryza sativa)accessions collected worldwide identified OsSPL10 and OsWOX3B as regulators of trichome development in rice.Here,we report that OsSPL10 acts as a transcriptional regulator controlling trichome development.Haplotype and transient expression analyses revealed that variation in the approximately 700-bp OsSPL10 promoter region is the primary cause of the glabrous phenotype in the indica cultivar WD-17993.Disruption of OsSPL10 by genome editing decreased leaf trichome density and length in the NIL-HL6 background.Plants with genotype OsSPL10^(WD-17993)/HL6 generated by crossing WD-17993 with NIL-HL6 also had fewer trichomes in the glumes.HAIRY LEAF6(HL6)encodes another transcription factor that regulates trichome initiation and elongation,and OsSPL10 directly binds to the HL6 promoter to regulate its expression.Moreover,the transcript levels of auxin-related genes,such as OsYUCCA5 and OsPIN-FORMED1b,were altered in OsSPL10 overexpression and RNAi transgenic lines.Feeding tests using locusts(Locusta migratoria)demonstrated that non-glandular trichomes affect feeding by this herbivore.Our findings provide a molecular framework for trichome development and an ecological perspective on trichome functions.