A cis regulatory element in the TAPNAC promoter directs tapetal gene expression.

The tapetum is a single cell layer surrounding the anther locule and its major function is to provide nutrients for pollen development. The ablation of tapetal cells interferes with pollen production and results in plant male sterility. In spite of the importance of this tissue in the quality and production of pollen grains, studies on promoter gene regulation of tapetal expressed genes are very few and there are no reports on specific cis regulatory sequences that control tapetal gene expression. We have identified a NAC gene, (At1g61110), specifically expressed in the Arabidopsis tapetum via transcriptional profiling. The TAduanyu1535C promoter was studied in detail to identify cis regulatory sequences that confer tapetal specific expression. For this purpose, TAduanyu1535C promoter elements were fused to the β-glucuronidase (GUS) reporter gene, and spatial and temporal GUS expression was monitored. The results showed that TAduanyu1535C promoter-driven GUS expression emulates the expression of TAduanyu1535C mRNA in anthers. A conserved TCGTGT motif was identified in the TAduanyu1535C promoter and other tapetal expressed promoters. The TCGTGT motif enhances GUS expression in anthers of transgenic plants but only in the context of the TAduanyu1535C promoter proximal region.

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