Wheat NAC transcription factorNAC5-1is a positive regulator of senescence

Abstract

Wheat (Triticum aestivum L.) is an important source of both calories and protein in global diets, but there is a trade-off between grain yield and protein content. The timing of leaf senescence could mediate this trade-off as it is associated with both decline in photosynthesis and nitrogen remobilisation from leaves to grain. NAC transcription factors play key roles in regulating senescence timing. In rice, OsNAC5 expression is correlated with earlier senescence, but the role of the wheat ortholog in senescence had not been characterised. We verified that NAC5-1 is the ortholog of OsNAC5 and that it is expressed in senescing flag leaves in wheat. To characterise NAC5-1, we combined missense mutations in NAC5-A1 and NAC5-B1 from a TILLING mutant population and overexpressed NAC5-A1 in wheat. Mutation in NAC5-1 was associated with delayed onset of flag leaf senescence, while overexpression of NAC5-A1 was associated with slightly earlier onset of leaf senescence. DAP-seq was performed to locate transcription factor binding sites of NAC5-1. Analysis of DAP-seq and comparison with other studies identified putative downstream target genes of NAC5-1 which could be associated with senescence. This work showed that NAC5-1 is a positive transcriptional regulator of leaf senescence in wheat. Further research is needed to test the effect of NAC5-1 on yield and protein content in field trials, to assess the potential to exploit this senescence regulator to develop high-yielding wheat while maintaining grain protein content.

Transcriptional Control of Seed Life: New Insights into the Role of the NAC Family

“…As demonstrated throughout this review, the LS process is of singular importance in the life of plants and therefore is extensively studied (i.e., OSNAC5). In the current year, the Borrill group achieved a significant breakthrough in the NACs-LS relationship in wheat (Triticum aestivum L.) [268]. Thus, TaNAC5-1, an ortholog of OSNAC5 expressed in senescing flag leaves, acts as a positive regulator of LS.…”

“…Unfortunately, the DAP-seq analysis for TaNAC5-1 yielded limited information. Nonetheless, two serine peptidases and an α/β gliadin gene were identified as potential targets of TaNAC5-1 [268].…”