Preliminary Study On The Mechanism Of Greening Phenomenon Of Arabidopsis Thaliana Albino Mutant Pde191in Sucrose-containing Medium

Some of the Arabidopsis pigment-deficient mutants can become green in sucrose-containing medium. We obtained a T-DNA insertion mutant of PDE191, which is a mitochodrial transcription termination factor in Arabidopsis. The pde191mutant displayed albino phenotype on medium without sucrose, but it could turn green when exogenous sucrose was supplemented. This research is aimed at exploring the mechanism of greening process in pdel91. PDE191is involved in the transcription termination of rpoA. The transcription termination of rpoA in greening pde191mutants showed no obvious differences compared with albino pde191. To uncover the role of sucrose in the greening process, we first replaced sucrose with palatinose that can not be metabolized and found that albino pdel91could not turn green. Then, we added sucrose and KNO3into medium simultaneously and found that pde191could turn green. These results showed that sucrose enter metabolic pathway to support the greening process of pde191. To further confirm this conclusion, we replaced sucrose with pyruvic acid that is an intermediate in glycolysis, the pde191could turn green. On the other hand, we cultivated pde191with sucrose and2-Deoxy-D-glucose that is an inhibitor in glycolysis, the pde191could not turn green. The results further indicated that sucrose enter metabolic pathway to support the greening process of pde191. In addition, the activity level of plastid-encoded polymerase (PEP) is essential for chloroplast development. We detected the transcription level of PEP-dependent genes between albino pde191and greening pdel91,during the different development stages. The result show that the PEP-dependent gene expressions in greening pde191is higher than that in albino pde191. Then, the PEP-dependent gene expressions were analyzed among two complete albino mutants (pdm1and ptac7), two delayed greening mutants (Jln2and pde191), we found that the PEP-dependent gene expression level in pde191is similar to that in fln2, but is higher than that in pdml and ptac7, which suggested that PEP activity is essential for greening process. We also detected the accumulation of rubisco subunits, rbcL and rbcS. The result indicated that pde191cultivated with sucrose accumulated rbcL and rbcS slowly. Taken together we think that greening process need energy supplied by sucrose to maintain the PEP activity which will facilitate chloroplast development and delayed greening of pdel91mutant.