Natural Variation of StNADC Regulates Plant Senescence in Tetraploid Potatoes (Solanum tuberosum L.).

Senescence impacts plant growth and yields in tetraploid potatoes (Solanum tuberosum L.). Because of their homogenous tetraploid features, it is a major challenge to understand the genetic basis and molecular mechanisms of senescence. Here, we identified a novel central senescence regulator (Nicotinate-nucleotide pyrophosphorylase QPT/StNADC) through map-based cloning. Overexpression of StNADC(Z3) accelerated senescence in the late-senescence variety, with NAD content declining by around 40%. CRISPR/Cas9-induced StNADC mutant cr2-11 exhibited extremely early senescence, and the NAD content was reduced by 87% along with reduced chlorophyll content and photosynthesis. Moreover, the downstream products of the NAD synthesis pathway, such as NaMN, NAD, or niacin, can refresh the cr2-11 mutant to grow normally. Further, the transcriptomics and metabolomics data unveiled that the disrupting of StNADC impairs NAD metabolism, accelerating plant senescence through multiple biological levels. Our results show that StNADC is indispensable for NAD synthesis, and targeting the StNADC-mediated NAD synthesis pathway could be a useful strategy to regulate senescence in potato breeding preprograms.