The NAC Transcription Factor ANAC087 Induces Aerial Rosette Development and Leaf Senescence in Arabidopsis

Abstract

CmNACP1 mRNA has been shown to move long distance through the phloem in <i>Cucurbita maxima</i> (pumpkin) and through a graft junction. Whereas the phloem transport of several different mRNAs has been documented in other systems as well, its function remains, for most of these RNAs, largely unknown. To gain insight into the possible role of these RNAs, we searched for the closest homologs of <i>CmNACP1</i> in Arabidopsis, a model plant much more amenable for analysis. A phylogenetic approach using the predicted NAC domain indicated that ANAC059, ANAC092, ANAC079, ANAC100, ANAC046, and ANAC087 form a single clade with CmNACP1. In the present work, we analyzed the possible function of the <i>ANAC087</i> gene in more detail. The promoter region of this gene directed expression in the vasculature, and also in trichomes, stem, apexes, and developing flowers which supports the notion that <i>ANAC087</i> and <i>CmNACP1</i> are orthologs. Overexpression of the <i>ANAC087</i> gene induced increased branching in inflorescence stem, and also development of ectopic or aerial rosettes in T1 and T2 plants. Furthermore, overexpression of <i>ANAC087</i> leads to accelerated leaf senescence in 44 days post-germination (dpg). Interestingly, a similar phenotype was observed in plants expressing the <i>ANAC087</i> gene upstream region, also showing an increase in <i>ANAC087</i> transcript levels. Finally, the results shown in this work indicate a role for <i>ANAC087</i> in leaf senescence and also in rosette development.