ABSTRACT
Development of plant organs is a highly organized process. In Arabidopsis, proper root development requires that distinct cell types and tissue layers are specified and formed in a restricted manner in space and over time. Despite its importance, genetic controls underlying such regularity remain elusive. Here we found that WIP genes expressed in the embryo and suspensor functionally oppose those expressed in the surrounding maternal tissues to orchestrate cell division orientation and cell fate specification in the embryonic root, thereby promoting regular root formation. The maternal WIPs act non-cell autonomously to repress root cell fate specification through SIMILAR TO RADICAL-INDUCED CELL DEATH ONE (SRO) family members. When losing all WIPs, root cells divide irregularly in the early embryo, but this barely alters their fate specification and the morphology of post-embryonic roots. Our results reveal cross-communication between the embryonic and maternal WIPs in controlling root development.
Subject(s)
Arabidopsis Proteins , Arabidopsis , Arabidopsis/metabolism , Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , Cell Differentiation , Cell Division/genetics , Gene Expression Regulation, Plant , Plant Roots/metabolism , Plants/metabolismABSTRACT
In cucurbits, CmWIP1 is a master gene controlling sex determination. To bring new insight in the function of CmWIP1, we investigated two Arabidopsis WIP transcription factors, AtWIP1/TT1 and AtWIP2/NTT. Using an inducible system we showed that WIPs are powerful inhibitor of growth and inducer of cell death. Using ChIP-seq and RNA-seq we revealed that most of the up-regulated genes bound by WIPs display a W-box motif, associated with stress signaling. In contrast, the down-regulated genes contain a GAGA motif, a known target of polycomb repressive complex. To validate the role of WIP proteins in inhibition of growth, we expressed AtWIP1/TT1 in carpel primordia and obtained male flowers, mimicking CmWIP1 function in melon. Using other promoters, we further demonstrated that WIPs can trigger growth arrest of both vegetative and reproductive organs. Our data supports an evolutionary conserved role of WIPs in recruiting gene networks controlling growth and adaptation to stress.
Subject(s)
Arabidopsis Proteins/genetics , Arabidopsis/genetics , Flowers/growth & development , Intracellular Signaling Peptides and Proteins/genetics , Transcription Factors/genetics , Arabidopsis/growth & development , Arabidopsis Proteins/metabolism , Flowers/genetics , Gene Expression Regulation, Plant , Intracellular Signaling Peptides and Proteins/metabolism , Transcription Factors/metabolismABSTRACT
In angiosperms, sex determination leads to development of unisexual flowers. In Cucumis melo, development of unisexual male flowers results from the expression of the sex determination gene, CmWIP1, in carpel primordia. To bring new insight on the molecular mechanisms through which CmWIP1 leads to carpel abortion in male flowers, we used the yeast two-hybrid approach to look for CmWIP1-interacting proteins. We found that CmWIP1 physically interacts with an S2 bZIP transcription factor, CmbZIP48. We further determined the region mediating the interaction and showed that it involves the N-terminal part of CmWIP1. Using laser capture microdissection coupled with quantitative real-time gene expression analysis, we demonstrated that CmWIP1 and CmbZIP48 share a similar spatiotemporal expression pattern, providing the plant organ context for the CmWIP1-CmbZIP48 protein interaction. Using sex transition mutants, we demonstrated that the expression of the male promoting gene CmWIP1 correlates with the expression of CmbZIP48. Altogether, our data support a model in which the coexpression and the physical interaction of CmWIP1 and CmbZIP48 trigger carpel primordia abortion, leading to the development of unisexual male flowers.
