Two Nucleoporin98 homologous genes jointly participate in the regulation of starch degradation to repress senescence in Arabidopsis
Abstract Background: Starch is synthesized during the day for temporary storage in leaves and then degraded during the subsequent night to support plant growth and development. Impairment of starch degradation leads to stunted growth, even senescence and death. The nuclear pore complex is involved in many cellular processes, but its relationship with starch degradation is unclear until now. We previously identified that two Nucleoporin98 (Nup98) genes (Nup98a and Nup98b) redundantly regulate flowering through CONSTANS (CO) independent pathway in Arabidopsis thaliana. The nup98a-1 nup98b-1 double mutant also shows severe senescence phenotypes. Results: We find that Nucleoporin 98 (Nup98) participates in the regulation of sugar metabolism in leaves and in turn involves in senescence regulation in Arabidopsis. We show that Nup98a and Nup98b redundantly function in the different steps of starch degradation and the nup98a-1 nup98b-1 double mutant accumulates more starch than wild type plants and has a severe early senescence phenotype compared to wild type plants. The expression of marker genes related to starch degradation is impaired in the nup98a-1 nup98b-1 double mutant, and marker genes of carbon starvation and senescence express earlier and in higher abundance in the nup98a-1 nup98b-1 double mutant than in wild type plants, suggesting that abnormality of energy metabolism is the main cause of senescence of the nup98a-1 nup98b-1 double mutant. Addition of sucrose to the growth medium rescues early senescence phenotypes of the nup98a-1 nup98b-1 mutant. Conclusions: Our results provide a line of evidence on a novel role of the nuclear pore complex in energy metabolism related to growth and development, in which Nup98 functions in starch degradation conferring growth regulation in Arabidopsis.