Screening Of Tumor-like Stem Swelling Related Genes In Tuber Mustard (Brassica Juncea) And Its Germplasm Innovation

Tuber mustard (Brassica juncea Coss. var. tumida Tsen et Lee), a variety in the species Brassica juncea and belonging to the genus Brassica in the Cruciferae family, is an economically important agricultural crop cultivated in China. Its swollen stems are used as excellent raw materials for processing pickled mustard tuber which is famous for its fresh, tender, fragrant, crisp characteristic. Promoting the development of tuber mustard industry is beneficial to increasing the income of the farmers, the efficiency of agriculture and accelerating agricultural economic development. In present study two aspects below were focused on:1. Analysis of gene different expression during stem swelling for clarifying the molecular regulation mechanism.2. Breeding new germplasm for foundation theories research and breeding practices. The results are summarized as follows:(1) The changes of stem volume, fresh weight, length, average transverse during stem develop-ment were analyzed. The results showed that tuber mustard grew rapidly from stage Ⅲ. Thus, Stage Ⅲ seemed like a turning point of stem development.(2) Gene different expression was studied based on cDNA-AFLP method.30TDFs which showed specific expression pattern were isolated. The nucleotide sequences of them were searched against various databases and described based on previously reported gene function. The TDFs that encoded TDF3、TDF6、TDF14、TDF15、TDF16、TDF21specifically expressed during the early stages perhaps were required for stem swelling induction. The rest of TDFs specifically expressed during the latter stages, were most likely to represent candidate genes with potential function during stem swelling.(3) Complete DNA sequence of BjAPY gene,2712bp in length, consisting of nine exons and eight introns was isolated. The CDS was1521bp encoding a putative membrane-bound apyrase. An890bp upstream sequence from the transcription start site was assigned as the candidate BjAPY promoter region, and it was submitted to PlantCARE to detect putative cis-elements involved in the regulation of BjAPY expression. The results implied that BjAPY was under the control of hormone and involved in the responses to light, low temperature and other abiotic stresses. (4) Quantitative real-time RT-PCR results showed that BjAPY expressed stably, at a relatively low level in leaf during six stages. By contrast, in stem, BjAPY had much higher expression level. As a whole, BjAPY expression increased from stage Ⅰ to stage Ⅳ, kept a relatively high level at stage Ⅴ, then decreased at stage Ⅵ. Gene expression analysis showed the expression of BjAPY was lowest in P4, and highest in P1(a part of nodule that irregularly bulged). These results indicated BjAPY was required for both stem rapidly swelling and nodule rapidly growth. The expression level of BjAPY in MD and SD were significantly higher than that in LD. Expression level of BjAPY in SD was highest. Gene expression analysis also showed that the expression level of BjAPY in low temperature(14℃/12℃) was much higher than that in high temperature. Thus, it seemed likely that both temperature and photoperiod could regulate BjAPY expression.(5) A line was selected from the sexual progenies of chimera TTC, which showed the potential to be used as an excellent material for breeding tuber mustard variety of processing type. This line with undulate leaf margin was erect and strong, grow vigorously. The tumor-like stem was flat with several small round nodules. The depth and width of ditch was small. The tumor-like stems was away from the ground. Field investigations indicated that this line showed some resistance to soft rot.(6) A line characterized with petals variation was also selected from the sexual progenies (GS1) of chimera TTC. Some flowers of this line were usually apetalous or showed some filiform petals. Further experiments show these variations can be inherited. Studies on this line may give a new insight to the molecular mechanism of inheritable variation induced by grafting chimeras between Brassica juncea and Brassica oleracea. And this material also can be used for apetalous rape (Brassica juncea) variety breeding.(7) Hybridization between tuber mustard and red leaf mustard was made. Hybrid F1all had red leaf. And red leaf plants to green leaf plants ratio was3:1in hybrid F2. The results suggested that red leaf trait was controlled by a single dominant gene. We also selected plant which had red leaf (homozygosis) and tumor-like stem for backcross and red leaf tuber mustard breeding...