Construction of PEG-mediated Genetic Transformation and Gene Knockout System in Fusarium oxysporum f. sp.cubense Tropic Race 4

Fusarium wilt of banana, caused by Fusarium oxysporum f. sp. cubense tropic race 4(Foc TR4), is a typical vascular and soil-borne disease which has significantly threatened the sustainable development of banana industry. In order to reveal the infection process and pathogenesis of Foc TR4, the young mycelia(66.7 mg/ml) of wild-type strain of Foc TR4(WT-Foc TR4) cultured for 18-20 h were lysed with enzyme mixture for protoplast formation, which consisted of 25 mg/ml driselase, 0.4 mg/ml chitinase, 15 mg/ml lysing enzyme and 1.2 mol/L potassium chloride. The resulted protoplasts of 2×10~7 cells/ml were used to test the efficiency of transformation mediated by polyethylene glycol, and up to 9 transformants per microgram of DNA were obtained. AmCyan, RFP and YFP genes were stably transferred into the WT-Foc TR4, separately, using the protoplast transformation system. The gene FoOCH1 encoding α-1, 6-mannosyltransferase in the WT-Foc TR4 was knocked out using the split-marker recombination technology. The genetic transformation and gene knockout system in this pathogen lays a foundation for the study of functional genomics and plant-pathogen interactions.

Phylogenetic Analysis among Maize Exserohilum turcicum Isolates from Yunnan Province by RAPD

[ Objective ] This study aimed to investigate the genetic variation of Yunnan Exserohilum turcicum isolates from molecular level, and provide theoretical basis for E. turcicum pathogenicity virulence differentiation and effective control of disease. [Method] A total of 56 E. turc/cum isolates from some areas of Yunnan Province were analyzed by RAPD. Based on the genetic distance, a dendrogram was constructed. [Result] Ten genetic groups were formed in the dendrogram. The RAPD groups had no obvious correlation with geographic origins. Some strains from one area were closely related to some from another area. [ Conclusion] Rich ge- netic variation existed among the tested isolates.

A functional centromere lacking CentO sequences in a newly formed ring chromosome in rice

An awned rice（Oryza sativa） plant carrying a tiny extra chromosome was discovered among the progeny of a telotrisomic line 2nt4L. Fluorescence in situ hybridization（FISH） using chromosome specific BAC clones revealed that this extra chromosome was a ring chromosome derived from part of the long arm of chromosome 4. So the aneuploidy plant was accordingly named as 2nt4L ring. We did not detect any Cent O FISH signals on the ring chromosome, and found only the centromeric probe Centromeric Retrotransposon of Rice（CRR） was co-localized with the centromere-specific histone CENH3 as revealed by sequential FISH after immunodetection. The extra ring chromosome exhibited a unique segregation pattern during meiosis, including no pairing between the ring chromosome and normal chromosome 4during prophase I and pre-separation of sister chromatids at anaphase I.