| Turfgrass germplasm resources are widely used in landscaping,soil and water conservation,wind and sand management,and saline-alkali land improvement in China.Temperature is an important environmental factor which affects the growth and ecological distribution of turfgrass.Turfgrass is divided into cool-season turfgrass and warm-season turfgrass.Bermudagrass is warm-season turfgrass which could exhibit supreme tolerance to high temperature with normal growth under 35-40 ?.However,bermudagrass can't grow normally in high-temperature area for a long time.Tall fescue is cool-season turfgrass,the continuous high temperature in summer inhibits the growth of tall fescue and reduces the quality of the lawn.Therefore,it is of great significance to characterize the tolerance of cool-season and warm-season grasses to high-temperature stress and dissect the underlying tolerance mechanisms.These analyses will provide clues to increase the heat tolerance of turfgrass with increased surviveal rate in hot summers.This study explored the physiological responses of warm-season turfgrass bermudagrass and cool-season turfgrass tall fescue to high-temperature stress.RNA-seq technology was used to identify transcriptional changes of bermudagrass and tall fescue in response to heat stress.Detailed functions of candidate F-box genes in response to heat stress were characterized.This data will illuminate the mechanism of protein ubiquitination modification in turfgrass response to high-temperature stress.The main findings of this paper are as follows:1.Characterize the physiological responses of warm-season turfgrass bermudagrass and cool-season turfgrass tall fescue to high-temperature stress(42 ?).In this study,warm-season bermudagrass 'Common' and cool-season tall fescue'Solara' were used as plant materials to determine the physiological changes under high-temperature conditions.The results show that the relative conductivity and proline content of tall fescue were significantly higher than those of bermudagrass.However,the content of MDA and SOD enzyme activity in tall fescue was lower than that of bermudagrass.These data showed that tall fescue undergoes physiological processes faster than bermudagrass under high temperature stress.Meanwhile,bermudagrass suffered less from high temperatures,resulting in relatively steady physiological level changes.2.In this study,we analyzed the transcriptomic changes of bermudagrass and tall fescue which were after treated in 2 h and 12 h high temperature.The results showed that 2140-5485 unigenes showed significant changes after heat treatment.Among them,118 and 51 unigenes were co-regulated in bermudagrass and tall fescue by high temperature.The GO enrichment analysis of DEGs in bermudagrass and tall fescue showed that the enriched GO terms were mainly involved in polysaccharide biosynthesis pathway,polysaccharide metabolism pathway,positive regulation of biology,and other aspects after 2 h of high-temperature treatment.The enriched GO terms in bermudagrass and tall fescue after 12 h of high-temperature treatment were far-infrared signal,dextran biosynthetic pathway,synthetic pathways related to photoperiod and flower synthesis,etc.F-box and RING U-box genes encoding E3 ligase were extensively changed in both turfgrasses under heat condition.3?The heat resistance function of F-box gene in bermudagrass and tall fescue was analyzed.The E3 ubiquitin ligase F-box gene that was up-regulated at 2 h and 12 h in both bermudagrass and tall fescue was selected as candidate genes for functioanal analysis.The q PCR results showed that the expressions of Cd F-box1 and Fa F-box1 were significantly up-regulated after 2h and 12 h heat treatment.Amino acid alignment showed that Cd F-box1 and Fa F-box1 were highly conserved.Additionally,C4 plant bermudagrass and C3 plant tall fescue had specific amono acid sequences in F-box protein.Cd F-box1 and Fa F-box1 genes were tranformed into model plant Arabidopsis.After high temperature treatment,the expression level of Cd F-box1 and Fa F-box1 increased in transgenic plants.Quantitative RT-PCR results showed that Fa F-box1 and Cd F-box1 are highly expressed in transgenic plants.After high temperature treatment,the transgenic plants had less senescence and dead leaves than wild-type plants,which indicated that the transgenic plants showed improved heat tolerance when compared to wild-type plants.Using transiently transformed tobacco,we observed that the majority of Cd F-box1 was localized in the nucleus.The FPNI-PCR was used to clone the promoter regions of the Cd F-box1 and Fa F-box1 genes.Motifanalysis results show that the elements including ABRE and HSE elements were presented in Cd F-box1 promoter,while only HSE element was pesented in the promoter of Fa F-box1.Using Fa F-box1 as the bait,the c DNA yeast library was screened for identification of interaction proteins.The results showed that several candidate genes includin Psa F-c163080 and CAB-c157615 were mainly involved in photosynthesis.These results indicated that F-box might regulate turfgrass heat tolerance through ubiquitination of proteins in photosynthesis pathways. |
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