The Research Of Sscd1Cell Death In Arabidopsis

In previous study, we’ve isolated an Arabidopsis (Arabidopsis thaliana) short-day sensitive cell death1(sscd1) mutant that displayed a spontaneous wilting under short-day conditions (8h light/16h dark). If the sscd1seedings were geminated directly under short-day condition, the leaves of sscd1were dead. If it geminated under long-day condition, then transferred to short-day, the leaves of sscd1were partial wilted or whitened. It was proved that sscd1wilted leaves were dead by Trypan blue staining, but it couldn’t be stained when totally whitened.The SSCD1gene was cloned via a map-based cloning approach and found to encode an Arabidopsis putative FAH (fumarylacetoacetate hydrolase, FAH). Tyr degradation plays an important role in animal metabolic and blockage of it results in metabolic disorder diseases. However, the role of the Tyr degradation pathway in plants is still unknown. The accumulation of MAA and FAA, resulting from the loss of FAH, would lead to abnormal metabolism of these compounds, both of which wew reduced to succinylacetoacetate that was then converted to succinylacetone. The HGO, an enzyme upstream of FAH in the Tyr degradation pathway, was essential for the catalysis of homogentisate into MAA and FAA. To testify whether the accumulation of metabolic intermediate was the reason sscd1display spontaneous cell death, we generated the sscd1hgo double mutant through genetic crossing of sscdl-1with hgo-1. Phenotypic analysis showed that the sscdl hgo-1double mutant did not display the cell death phenotypes under short-day condition, we proved this result further by adding exogenous SA (succinylacetone) to Arabidopsis, the cell death phenotype Col-0displayed was as same as sscd1. Moreover, we found that application of succinylacetone was able to significantly exacerbate the cell death of the sscd1mutant under short-day condition. Taken together, these results demonstrated that the accumulation of the metabolic intermediates, including succinylacetone, causes the cell death phenotype in the sscd1mutant.Besides, we found supplementation of high-concentration sucrose repressed the lethal phenotype of sscd1.we provided a new perspective to insight to the relationship among sucrose metabolic, Tyr degradation and programmed cell death.These results demonstrate that disruption of FAH leads to cell death in Arabidopsis and suggest that the Tyr degradation pathway is essential for plant survival under short-day condition.