Chen Rukai

Differential Gene Expression in Sugarcane in Response to Challenge by Fungal Pathogen Ustilago scitaminea Revealed by cDNA-AFLP

Differential gene expression in sugarcane during sugarcane-Ustilago scitaminea interaction was conducted in a smut-resistant genotype. Using cDNA-AFLP along with silver staining, a total of 136 transcript-derived fragments (TDFs) were found to be differentially expressed in response to challenge by U. scitaminea. Forty TDFs, 34 newly induced plus six with obvious upregulated expression after infection, were sequenced and validated by RT-PCR analysis. These results demonstrated that the expression of 37 out of these TDFs in RT-PCR analysis was consistent with that in cDNA-AFLP analysis. Based on BlastX in NCBI, 28 TDFs were assumed to function in sugarcane under U. scitaminea stress. Analysis of expression profile of three TDFs revealed that they responded differently after infection with U. scitaminea, and the transcription was significantly enhanced. The response of two TDFs, SUC06 and SUC09, occurred before that of SUC10. This study enriches our knowledge of the molecular basis for sugarcane response to U. scitaminea infection.Differential gene expression in sugarcane during sugarcane-Ustilago scitaminea interaction was conducted in a smut-resistant genotype. Using cDNA-AFLP along with silver staining, a total of 136 transcript-derived fragments (TDFs) were found to be differentially expressed in response to challenge by U. scitaminea. Forty TDFs, 34 newly induced plus six with obvious upregulated expression after infection, were sequenced and validated by RT-PCR analysis. These results demonstrated that the expression of 37 out of these TDFs in RT-PCR analysis was consistent with that in cDNA-AFLP analysis. Based on BlastX in NCBI, 28 TDFs were assumed to function in sugarcane under U. scitaminea stress. Analysis of expression profile of three TDFs revealed that they responded differently after infection with U. scitaminea, and the transcription was significantly enhanced. The response of two TDFs, SUC06 and SUC09, occurred before that of SUC10. This study enriches our knowledge of the molecular basis for sugarcane response to U. scitaminea infection.

Molecular Identification and Genetic Diversity Analysis of Chinese Sugarcane (Saccharum spp. Hybrids) Varieties using SSR Markers

Sugarcane (Saccharum spp. hybrids) is an important sugar and renewable bio-energy crop with a high aneu-polyploidy and complex genome. The complex characteristics of sugarcane genome enhance the difficulty of selecting elite varieties in sugarcane breeding program. The objectives of this study were to establish the molecular identities (ID) of 91 nationally or provincially released Chinese sugarcane varieties and to evaluate the extent of genetic diversity among these varieties using SSR DNA markers and two fingerprinting systems, i.e., capillary electrophoresis (CE) and polyacrylamide gel electrophoresis (PAGE). A total of 151 SSR alleles together with 20 new alleles were detected by CE and 117 SSR alleles were detected by PAGE. Primer pairs SMC336BS, SMC31CUQ, and SMC597CS amplified more than eight alleles detectable by either CE or PAGE. Polymorphism information content (PIC) values of the SSR markers varied from 0.71-0.98 with an average of 0.90 for CE, or from 0.55-0.95 with an average of 0.84 for PAGE. UPGMA method classified the 91 varieties based on the CE data into four major groups with pair-wise similarity coefficients ranging from 58% to 95%. The genetic similarity estimates within and between the four groups varied from 0.31 to 0.87, with a mean of 0.49. Our results illustrated that the 21 SSR primer pairs in combination with CE or PAGE detection system could be a very useful working tool for molecular identification of sugarcane varieties, genetic diversity assessment, and parental selection in sugarcane breeding.

Isolation and Characterization of Disease Resistance Gene Analogs from Erianthus arundinaceus cDNA

Plant disease resistance genes (R-genes) encode some conserved motifs. According to the conserved motifs present in the known NBS-LRR R-gene sequences and R gene analogs (RGAs), several degenerate primers were designed and applied in the RGA isolation from Erianthus arundinaceus using PCR approach. In total, 6 RGAs were successfully obtained, with GenBank accession numbers of EU685835, EU685836, EU685837, EU685838, EU685839, and EU685840. Multiple alignments showed that the encoding sequences of the six clones were highly conserved and strikingly similar to the eleven most typical NBS-LRR type R-gene peptide sequences, especially at the four NES motifs of P-loop. kinase-2, kinase-3a, and HD. The identity percentage at the amino-acid level ranged from 8.3% to 93.0% among all 17 sequences tested and from 30.5% to 45.6% among the six RGAs cloned in this study. The results of cluster analysis and the existence of an aspartic acid residue (D) at the final residue position of the kinase-2 motif also indicated that all of E. arundinaceus RGAs might belong to non-TIR group. The Real-time PCR results showed that all of the RGAs were constitutively expressed in roots, stalks and leaves of E. arundinaceus, and their expression could be up-regulated in leaves by the exogenous signal molecules SA and H2O2. Therefore, it suggested that E. arundinaceus RGAs might play important roles in disease resistance in an SA- and H2O2-dependent defense response pathway. Further studies should aim to clone full-length R-genes in E. arundinaceus and characterize their functions in defense responses.