Screening of potential IL-tolerant cellulases and their efficient saccharification of IL-pretreated lignocelluloses.

Lignocellulosic biomass as one of the most abundant and renewable resources has great potential for biofuel production. The complete conversion of biomass to biofuel is achieved through the effective pretreatment process and the following enzyme saccharification. Ionic liquids (ILs) are considered as a green solvent for lignocellulose pretreatment. However, ILs exhibit an inhibitory effect on cellulase activity, leading to a subsequent decrease in the efficiency of saccharification. The screening of new potential IL-tolerant cellulases is important. In the current study, a fungal strain with a relatively high cellulase production was isolated and identified as Penicillium oxalicum HC6. The culture conditions were optimized using corn stover and peptone as the carbon source and nitrogen source at pH 4.0 and 30 °C with an inoculation size of 2% (v/v) for 8 days. It was found that P. oxalicum HC6 exhibited potential salt tolerance with the increase of the enzyme production at a salt concentration of 5.0% (w/v). In addition, high enzyme activities were obtained at pH 4.0-6.0 and 50-65 °C. The crude enzyme from P. oxalicum HC6 with good thermal stability was also stable in the presence of salt and ILs. Good yields of reducing sugar were obtained by the crude enzyme from P. oxalicum HC6 after the saccharification of corn stover that was pretreated by ILs. P. oxalicum HC6 with potentially salt-tolerant and IL-tolerant enzymes has great potential application in the enzymatic saccharification of lignocellulose.

Genome-wide identification of wheat (Triticum aestivum) expansins and expansin expression analysis in cold-tolerant and cold-sensitive wheat cultivars.

Plant expansins are proteins involved in cell wall loosening, plant growth, and development, as well as in response to plant diseases and other stresses. In this study, we identified 128 expansin coding sequences from the wheat (Triticum aestivum) genome. These sequences belong to 45 homoeologous copies of TaEXPs, including 26 TaEXPAs, 15 TaEXPBs and four TaEXLAs. No TaEXLB was identified. Gene expression and sub-expression profiles revealed that most of the TaEXPs were expressed either only in root tissues or in multiple organs. Real-time qPCR analysis showed that many TaEXPs were differentially expressed in four different tissues of the two wheat cultivars-the cold-sensitive 'Chinese Spring (CS)' and the cold-tolerant 'Dongnongdongmai 1 (D1)' cultivars. Our results suggest that the differential expression of TaEXPs could be related to low-temperature tolerance or sensitivity of different wheat cultivars. Our study expands our knowledge on wheat expansins and sheds new light on the functions of expansins in plant development and stress response.

[Identification of RAPD markers linked to the resistance gene Yr5 against wheat stripe rust with denaturing PAGE-silver staining].

RAPD analysis was performed between a near-isogenic line (NIL) Yr5/6 x Avocet S carrying the resistance gene Yr5 against wheat stripe rust and its susceptible parent Avocet S, using the Yr5 gene donor parent Triticum spelta album as control. Amplified DNA fragments were separated on 4% denaturing PAGE (polyacrylamide gel electrophoresis) and displayed by silver staining. Fifty to 100 bands were detected, 5 folds more than those revealed on agarose gels. A total of 240 random primers were screened, and 23 reproducible polymorphic DNA fragments were found, out of which 6 polymorphic bands appeared to be linked to Yr5 gene. Genetic linkage was tested on 121 segregating F2 plants derived from a cross between Avocet S and Yr5/6 x Avocet S. It was showed that the polymorphic DNA fragment S1320(207) was completely linked to Yr5 gene, and S1348(363) closely linked to Yr5 gene. The results suggested that using denaturing PAGE-silver staining could increase the level of DNA polymorphisms detected in wheat and also improve the repeatability of RAPD analysis.