| Potato(Solanum tuberosum L.)is a tuber bearing plant which belongs to the Solanaceae family.It has become the fourth largest food crop in the world after wheat.rice and maize.Chinese is the biggest potato production country in the world;it plays an important role in food security of our country.In recent years,global warming has intensified,high temperature stress has become one of the most important reasons that inhibits potato's growth,development,yield and quality.A sharp decline in production and a huge economic loss could be caused of the temperature reached to a higher level.Related research has shown that high temperatures can directly disrupt plant metabolism and damage cell structure.However,plants possess their own protection mechanism to protect themselves from the damage.In this study,potato variety "Minshu 1" was used to investigate the physiological and biochemical changes of plants under high temperature stresses,including morphological indexes,antioxidant indexes,photosynthesis index and related chlorophyll fluorescence parameters.Bioinformatics analyses of potato growth regulator(GRF)gene family and superoxide dismutase(SOD)gene family were carried out and the expression levels of selected gene under high temperatures were studied.1.Effects of high temperature stress on physiological indexes of potato plantsData on plant height,stem diameter,leaf length and width,leaf fresh weight and dry weight from the potato plants were collected.It was found that the growth of potato plants was significantly inhibited by high temperature stress.Plant height and stem diameter were smaller than those of the controls,leaves were smaller and shorter,fresh weight and dry weight were also decreased in the heat treated plants in comparison to the untreated plants.The antioxidant indexes which included superoxide anion(O2-),malondialdehyde(MDA),hydrogen peroxide(H2O2)and proline(Pro)and the activities of superoxide dismutase(SOD),peroxidase(POD),and catalase(CAT)of potato seedlings under the high temperature treatments were also measured.The results indicated that the contents of O2-,MDA,H2O2,and PRO were all increased during the examination period.The contents of SOD was rising first and then decreased;values of POD and CAT were decreased first and then increased.The accumulation of reactive oxygen species and increased membrane oxidation in potato seedlings were the reasons that may cause the damages to potatoes under high temperatures.Photosynthesis indexes showed that the contents of chlorophyll a,chlorophyll b,total chlorophyll and carotenoid were decreased,transpiration rate increased,net photosynthetic rate was decreased,stomatal conductance and intercellular carbon dioxide content were increased in the heat treated samples in comparison with the untreated samples.The chlorophyll fluorescence parameters showed that FO was increased,Fv/Fm was decreased,NPQ and qN were increased first and then decreased in the treated plants;even qP had no obvious changes,the ETR was decreased.It indicated that high temperature inhibited photosynthesis of seedlings leaves to some extent.2.Bioinformatics analysis and specific expression analysis of potato GRF transcription factorsTwelve potato GRF genes were obtained from the plant transcription Factor database(http://planttfdb.cbi.pku.edu.cn/).The bioinformatics analysis showed that the potato GRF family was the closest to the tomato GRF family,followed by that of Arabidopsis,and the relationship between rice and potato was far.StGRF6 contains only one intron,whereas the rest all have two or three introns.The domains of potato GRF genes are highly conserved,and every gene has a QLQ and a WRC domain.The expression of potato GRF genes under high temperature treatments were analyzed by real-time RT-qPCR,and the expression levels of StGRF1 and StGRF5 were significantly up-regulated,whereas the StGRF2,StGRF3,StGRF7,StGRF8 and StGRF10 genes were decreased.StGRF4,StGRF6 and StGRF9 gene showed no difference when compared with the controls.3.Bioinformatics analysis and specific expression analysis of potato SOD genesEight potato SOD genes were obtained from the NCBI database(https://www.ncbi.nlm.nih.gov/).The results of bioinformatics analysis showed that potato SOD genes had different protein length and poor stability,and they are all hydrophilic proteins.The similarity of these eight protein sequences was only 34.68%,so the 8 potato SOD genes had great differences in the number of amino acids and the structure of the proteins.Evolutionary tree analysis showed that Fe-SOD1,Fe-SOD2,Fe-SOD3,Fe-SOD4 and Mn-SOD were closely related,while SOD1,Cu/Zn-SOD1 and Cu/Zn-SOD2 were closely related.We studied the potato SOD genes expression under high temperatures by real-time RT-qPCR,and the results showed that the expression of SOD1 was increased in the early stage of the treatments;the expression of Fe-SOD1,Fe-SOD2,Fe-SOD3 and Fe-SOD4 were increased significantly,while the expression of Cu/Zn-SODl,Cu/Zn-SOD2 and Mn-SOD had no obvious changes,but the expression of Cu/Zn-SOD2 at 12 h without the heat treatment was about 2.22 times higher than that of the high temperature treated samples. |
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