Genetic Identification Of A New Tillering Gene Osrcn In Rice;Effects Of Steam Explosion And Tween 80 On The Enzymatic Saccharification And Ethanol Production Of Common Reed

Rice tillering has a direct effect on grain yield and biomass production.In this study,a new rice tillering gene OsRCN was identified by characterizing a novel mutant.The main results are described below:1.Overexpression(OE)of OsRCN leads to much increased tilling number in the transgenic plants compared with wild type(WT).2.Compared with WT,the homozygote(Ho)of rcn mutant showed much reduced tilling number,but had a similar height and panicle phenotype.In particular,the rcn plants did not have any tilling aboveground.3.The effective tillering number of rcn mutant is significantly decreased compared with WT.4.The rcn mutant showed a slowing initiation of tillering,but the genetic crossed plant between Ho of rcn and WT can restore the phenotype as WT.5.The phenotypes of rcn's F2 populations were segregated.6.RNA transcript analysis confirmed a high rcn expression level in the overexpressed transgenic plant without any expression in the mutant.7.The results suggest that OsRCN gene play a role in controlling the initiation of rice tillering.Common reed is one of the most widespread wetland plants with high biomass yield for biofuel purpose.In the study,steam explosion and other pretreatments were performed for enhancing the sequential biomass enzymatic hydrolysis in the reed samples.As a result,the steam explosion and Tween 80 supplement with cellulase enzymes could greatly enhance the enzymatic saccharification and ethanol production.The sequential four pretreatments with the steam-exploded residues exhibited a significantly positive correlation between the soluble cellulase enzymes concentrations and hexoses yields at p<0.01 level with high R2 value at 0.84,whereas the raw materials had a non-correlation.It suggested that the soluble cellulase enzymes should be not much absorbed with noncellulosic polymers(lignin,hemicellulose)in the steam-exploded residues,leading to an effective enzymatic hydrolysis of lignocelluloses.On the other hand,the lignin levels of the steam-exploded residues after various pretreatments,showed a negative correlation with the soluble cellulase enzyme concentrations at p<0.01 level with high R2 value at 0.84,but a non-correlation was found in the residues with Tween 80 supply,indicating that the Tween 80 should play a role in blocking lignin absorbing with cellulase enzymes in the steam-exploded residues.As a comparison,the hemicelluloses of the steam-exploded residues with Tween 80 were negatively correlated with the cellulase enzymes at p<0.01 level with extremely high R value at 0.98,whereas correlation was not found in the steam-exploded residues without Tween 80 supply,indicating that the Tween 80 could disassociate hemicelluloses with lignin in the steam-exploded residues.Yeast fermentation was further performed for bioethanol production.Three pretreatments were selected for relatively high bioethanol yields:(1)10%CaO pretreatment with 1%Tween 80 at 12%(%dry matter);(2)The steam-explosion pretreatment with 1%Tween 80 at 17%;(3)5%CaO pretreatment with the steam-exploded residues with 1%Tween 80 at 19%.