Functional Study Of An Acid Phosphatase Gene SbAP1 From Sorghum Bicolor And Preliminary QTLmapping Of Three Important Agronomic Traits In Sweet Sorghum

With the rapid development of the world economy, the world is experiencing an increasingly serious energy crisis. Now all countries are beginning to look for new sources of energy to replace the existing fossil fuels. As a new energy, bio-energy has became an important way to alleviate the world energy crisis because of its great advantages such as abundance, low-pollution and renewable. But high level of lignin in biomass feedstock is becoming one of the major limiting factors affecting the efficiency of cellulose degradation in cellulosic ethanol industry. The lignin not only increases the degree of the pretreatment and the amount of cellulase, but also inhibits the activity of the cellulase. So further study of the molecular mechanism of synthesis and regulation of plant lignin, can efficiently control the synthesis of plant lignin thereby improving the production of cellulosic ethanol.Sorghum is an important bio-energy plant. In preliminary experiment suppression subtractive hybridization (SSH) combined with cDNA microarray profiling was performed to identify the differentially expressed genes in 13 sorghum bmr mutants. In this paper, we studied one of the acid phosphates gene SbAP1. The results showed that:over expression of SbAPl can significantly improve the transgenic Arabidopsis lignin content and the expression of multiple key genes in lignin synthesis pathway is also significantly enhanced (for example AtHCT, AtCCOAOMT, AtF5H). In addition, SbAPl can promote the development of plant, increase the diameter and area of the seedling rosette leaves, and may contribute to its early flowering. However, over expression of SbAPl does not improve the ABA resistance of transgenic Arabidopsis, and shows no obvious reaction to NaCl, H2O2, and mannitol. The exact mechanism of SbAPl affecting lignin synthesis whether by intracellular calcium signaling system, hormones (salicylic acid, ABA, etc) or related transcription factors needs further experimental proof.The heterosis of sweet sorghum is obvious. In this paper, we choose sweet sorghum SI48 and male sterile lines Shi28A as parents for hybridization to obtain 445 F2 populations. Plurality agronomic traits (including plant height, stem diameter, plant fresh weight, brix, flowering period, the number of sections, seed weight, etc.) of each plant were counted. We screened out 307 pairs of polymorphic primers from 2980 pairs of sorghum SSR primers, then selected almost 100 pairs to detect the polymorphism of F2 populations, finally got 95 effective SSR markers. We used Mapmaker3.0 & Mapdisto to calculate genetic linkage map distance, and then constructed a linkage map for sorghum spanned a distance of 1459.5cM with an average distance between markers of 19.46cM. Based on the constructed linkage map, QTL mapping was conducted for three energy related traits of plant height, fresh weight and seed weight(Note:past master Wang DX and Li JJ involved in the completion of the work). We identified the major QTL for each trait, and found more than one trait QTL cluster co-localized on chromosome 6. In this paper, we analyzed the distribution and relevance of major QTL for each trait. The study laid the foundation for these major QTL fine mapping, map-based cloning and marker-assisted breeding research.