Characterization and physiological relevance of ZmNAC24 transcription factor and its relation to ZmPIP2;9

Details

Supervisors

Chaumont, François ; Teirlinckx, Estelle

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée

Abstract

Abiotic stress constitutes an important factor in plant development and thus in crop yield. Maize is one of the world’s most important crops and is an important subject for plant stress response studies, particularly regarding water regulation. Yet, among the various water regulatory mechanisms, knowledge is still limited about the regulation of aquaporin (AQP) gene expression. AQPs are a family of proteins that are largely responsible for the diffusion of water across cell membranes. The regulation of AQP gene expression is mediated through transcription factors (TFs), among them lies the NAC family. NAC TFs play major roles in plant growth and in responses to both biotic and abiotic stresses. In this work, a recently discovered AQP, ZmPIP2;9, was characterized by its sequence analysis in comparison with other members of its subfamily, the plasma membrane intrinsic proteins (PIPs). ZmPIP2;9 subcellular localization was then investigated through its transient expression in maize and N. benthamiana cells after fusion with a yellow fluorescent protein (YFP). As expected for a PIP aquaporin, ZmPIP2;9 was mainly localized in the plasma membrane. A previous genome-wide association study associated the expression of ZmPIP2;9 with a TF, ZmNAC24, and interestingly, ZmNAC24 regulatory elements were found in ZmPIP2;9 promoter. These data led us to conduct a transactivation assay to test the interaction between the ZmNAC24 and ZmPIP2;9 promoter. Two experiments were carried out and a significant increase of the ZmPIP2;9 promoter activity upon ZmNAC24 expression was measured in one of them. Furthermore, to study the physiological role of ZmNAC24 at the cell and plant levels, we designed constructs to overexpress ZmNAC24 in Arabidopsis thaliana. Transient expression in N. benthamiana allowed us to detect different unexpected ZmNAC24 protein products, depending on the promoter controlling the expression. This was thoroughly discussed.