Molecular Mechanism Of Slow Seedling Development Of Switchgrass And The Effect Of Storage Temperatures On Seed Germination

Switchgrass is a perennial herb distributed in North America and Central America,and it is considered to be an ideal bioenergy crop to replace food crops for bioethanol production due to its advantages of large biomass,rich cellulose,readily fermentability in ethanol production and excellent stress resistances.However,switchgrass exhibits serious seed dormancy,low rates of seedling establishment and grows slowly during the seedling period.These drawbacks make it typically out-competed by weeds,affect the seed development in the large-scale plantation.The transcriptomes from rapidly established(re)and slowly established(se)seedlings were compared using RNA-Seq technology to identify candidate genes involved in seedling establishment;The effects of different storage temperatures on switchgrass seed dormancy were analyzed by comparing the germination rate,germination index and germination potential.1.The transcriptomes of rapidly established(re)and slowly established(se)seedlings from one single plant were compared using RNA-Seq technology.Following de novo assembly,143,357 Unigenes were detected with an average length of 1,174 bp from total sequence reads of 60 gigabases,and the Unigenes were annotated.One hundred and twentyfive differentially expressed genes(DEGs)were obtained between re and se,including 94 genes upregulated and 31 downregulated in se relative to re.The most commonly assigned gene ontology annotations were “regulation of biological process”,“pigmentation,” and “response to stimulus.” Transcription factor analysis showed that 38 % of the DEGs identified as transcription factors belonged to the basic helix-loop-helix family.Ent-kaurene Synthase,the key enzyme in biosynthetic pathway of gibberellic acids(GAs),was found to be upregulated in re.The GAs level of re was higher than that of se.The analysis of DEGs implied that differences in plant hormone biosynthesis and signal transduction involving GAs,chloroplast proteins,metabolic energy allocation,and distinct response to environment could result in the different rates of seedling establishment in switchgrass.2.The results of the effects of different storage temperatures on switchgrass seed germination show that seed germination of switchgrass requires a certain accumulated temperature.If the storage temperature is 25 oC,the suitable processing time should be 90-120 days,and if the storage temperature is 30 oC,the suitable processing time should be 75-105 days.Switchgrass seed has not only physiological post-maturation,but also morphological post-maturation,which may be an important reason that leads to its deep dormancy.