Mustard Tumv Coat Protein Gene Cloning, Sequence Analysis, And Its Infection Of Plants, Biological Characteristics

Turnip mosaic virus (TuMV) is one of the most economically important plant virus in the world and has a wide host range of infecting plants in over 300 species. It naturally infects Brassica and other crops. The most serious TuMV infections have occurred in stem mustard (Brassica juncea van tsatsai), a very important vegetable in China, usually causing severe yield losses of 30-40%, and even up to 80 % by reducing plant growth.An isolate of turnip mosaic virus, named TuMV-HZZC, was obtained from naturally infected stem mustard, which did not infect either Nicotiana tobacwn or N. qlutinosa, but had high pathogenicity to cruciferous crops tested. The results from the present experiment indicated that TuMV and CMV can synergistically infect plants with aggravating symptoms, and a greatly increased symptom severity often occurred in cruciferous crops after infection by both TuMV and CMV in comparison with individual virus infection.CP gene of TuMV-HZZC was obtained by reverse transcription polymerase chain reaction and then cloned into a pMD 18-T vector. The nucleotide sequence of the cloned CP gene was sequenced. Comparison of the nucleotide sequence of TuMV-HZZC CP gene in pair with that of CP genes from others strains revealed that the homologies were of88.0%-97.6%, while at the amimo acid sequence level, the homologies were 90.7-96.5%. Therefore, we concluded that TuMV-HZZC belonged to one TuMV subgroup.TuMV infection inhibited stem mustard growth. Virus-infected plants had lower plant height, smaller leaf area and lower chlorophyll content, and showed a decreased net photosynthetic rate, stomatal conductance and transpiration rate as compared with that of control plants, but the intercellular CO2 concentration was higher in infected plant than in control plants. No great differences between infected and control intact leaves regarding chlorophyll a fluoresence parameters were observed.