Journal
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
Volume 23, Issue 19, Pages -Publisher
MDPI
DOI: 10.3390/ijms231911053
Keywords
OsSAC3; leaf senescence; sugar accumulation; xanthine dehydrogenase; uric acid; Oryza sativa
Funding
- Science Fund for Creative Research Groups of the Natural Science Foundation of Chongqing, China
- Fundamental Research Funds for the Central Universities [SWU-KQ22006]
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Research shows that xanthine dehydrogenase plays a crucial role in regulating leaf senescence in rice by influencing nitrogen metabolism and carbon metabolism. Mutant ossac3 with abnormal expression of OsSAC3 gene exhibits altered sugar accumulation, starch degradation enzyme activity, and carbohydrate distribution.
In both animals and higher plants, xanthine dehydrogenase is a highly conserved housekeeping enzyme in purine degradation where it oxidizes hypoxanthine to xanthine and xanthine to uric acid. Previous reports demonstrated that xanthine dehydrogenase played a vital role in N metabolism and stress response. Is xanthine dehydrogenase involved in regulating leaf senescence? A recessive early senescence mutant with excess sugar accumulation, ossac3, was isolated previously by screening the EMS-induced mutant library. Here, we show that xanthine dehydrogenase not only plays a role in N metabolism but also involved in regulating carbon metabolism in rice. Based on map-based cloning, OsSAC3 was identified, which encodes the xanthine dehydrogenase. OsSAC3 was constitutively expressed in all examined tissues and the OsSAC3 protein located in the cytoplasm. Transcriptional analysis revealed purine metabolism, chlorophyll metabolism, photosynthesis, sugar metabolism and redox balance were affected in the ossac3 mutant. Moreover, carbohydrate distribution was changed, leading to the accumulation of sucrose and starch in the leaves containing ossac3 on account of decreased expression of OsSWEET3a, OsSWEET6a and OsSWEET14 and oxidized inactivation of starch degradation enzymes in ossac3. These results indicated that OsSAC3 played a vital role in leaf senescence by regulating carbon metabolism in rice.
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