Full-length CDNA Cloning Of PHYA And PKS1and Their Primary Relationship With Stem Swelling Of Brassica Juncea

Brassica juncea, as an important stem food crop, is unique to China. Hot pickled tuber mustard made by swollen stem as raw material tastes good and is one of the world’s three famous pickles along with Germany pickled cabbage and Europe pickled cucumber with soy sauce. Tuber mustard is rich in nutrient whose protein, sugar, calcium and phosphorus levels are far more than those of congeneric cabbages. Therefore, Brassica juncea has a high edible and economic value. Nevertheless, the conditions of growth areas and planting time affect seriously the further improvement of Brassica juncea. Especially, neck hollow in its stem tumor during the growth process is an important reason for leading to its large-scale production reduction.In this study,13possible genes involved in stem swelling process have been screened out by comparing transcriptomes before and after Brassica juncea stem swelling. Among which, PKSl’s function is best-studied, which regulate the growth of plant as significant element during PHYA signal pathway by feedback control PHYA’s expression to regulate plant growth. Hence, Brassica juncea PHYA (BjPHYA) and PKSl (BjPKSl) was selected to elaborate their functions in Brassica juncea swelling process in this study. The study results are listed as the following:1. Rapid amplication of cDNA end was utilized to isolate BjPHYA and BjPKSl’s complete cDNA sequence and have been submitted to Genebank;2. Homology analysis by Blast showed that both BjPHYA and BjPKSl have higher homologous to AtPHYA and AtPKSl, respectively, in both nucleotide sequence and protein sequence. However, phylogenetic analysis revealed that BjPKSl and AtPKSl belong to different evolution line;3. RT-PCR was utilized to analyze BjPHYA and BjPKSl expression level at different stage during Brassica juncea stem swelling, the results shows that BjPKSl was higher during swelling than pre-swelling, while BjPHYA is in the opposite situation. And this result is consistent with Brassica juncea transcriptome analysis during stem swelling. Thus, we can speculate that BjPHYA and BjPKSlmight be involved in the regulation of stem swelling process;4. To analyze the function of BjPHYA and BjPKSl during Brassica juncea stem swelling process, two overexprssion vectors were constructed and transformed to Brassica juncea by Agrobacterium-mediated genetic transformation method. BjPHYA overexpression plants have different type of stems and late stem initiation time when comparing with the wild type. Furthermore, the overexpression of BjPHYA has lead to its dwarf, multi-branch, early flowering, narrow and dark green leaves and higher leaf density. These phenotypes above have proved that BjPHYA has similar functions with those PHYA in othe species. Meanwhile, over-expression of BjPKSl have proved that BjPKSl is similar to other species’ PKSl which participate in PHYA signal pathway to control plant height, pigmentation and tillering.The above results showed that BjPHYA and BjPKSl are homologous to AtPHYA and AtPKSl, respectively, which play similar roles in different plants. Significant different expression levels in tumorous stem mastard stem swelling process suggest that at least one of them participate in this process is an important regulator.