| As the global warming is projected to aggravate in the future,high temperature presents a serious challenge to rice production.Yangtze River basin and Hubei Province,well-known high temperature zone in the world,the improvement in heat-tolerance in rice has become an urgent issue.Currently,breeding for resistance to extremes of high temperature has been considered as the optimum approach.The premise of breeding for resistance to high temperature is needed that will give reliable,rapid assessment of the high temperature resistance.However,little information is available on the technique of assessment of the high temperature tolerance,and the progress in rice breeding for resistance to high temperature has been serious lagged behind.Some scientific methods aimed at assessment of high temperature tolerance have mainly been concentrated on single temperature to distinguish sensitive cultivars and tolerant cultivars in greenhouse or natural screening in the rice paddy.However,there are potential problems with single temperature method in the assessment of high temperature because of the uncertain threshold temperature.The screening results obtained from the two methods may be uncertainly,and the differences in heat-tolerance between varieties are also inaccurate.Hence,these ways cannot meet the requirement of rice varieties to high temperature.It has been reported that the difference of temperature tolerance among rice cultivars could be up to 4-6?.It is more likely to screen the threshold temperature of all tested varieties with proper cascade high-temperatures,and thus identify their tolerance accurately.In addition,many QTLs and SNPs of rice were found at present.However,due to the differences in materials and methods used by various research groups in the world,few well-known rice heat-resistant genes have been found.It is possible to identify accurately the expression of specific proteins in the anthers of the typical tolerant rice cultivars at the cascade temperature from the perspective of proteomics and the specific protein expression of rice at specific inflection temperature,and then deduce the specific genes and their loci effect.In this study,the varieties of N22,IR64,Quanliangyou 681 and Mianhui 101 were grown in the temperature and humidity controlled climate chamber in potted in the constant three years,2014,2015 and 2016.The genotypes contrasting in their salinity tolerance were selected.Simulate the weather factor of the typical local thermal hazard year,and carry out the cascade high temperature treatment.The results showed that three temperature gradients(daily maximum temperature of 33 ?,35 ? and 37 ?,respectively)were used to determine the fertilization rate,stigma pollination performance,anther cracking performance.The high temperature tolerance index and comprehensive high temperature tolerance index of each species were calculated,and the high temperature resistance of the tested varieties was evaluated.On the basis of this,seven rice varieties(materials)were screened for heat resistance.Based on the above experiment,a typical high temperature cultivar N22 and a sensitive cultivar Mianhui 101 were selected to study the anthers in the treatment stage.Samples were collected on the third day of the day,and the total protein was extracted.The changes in protein expression were identified by quantitative analysis and database search.The main results are as follows:1.2015-2016 2 years of joint data analysis showed that varieties in the control and the cascade of high temperature of the spike fertilization rate as the criteria.variety N22 comprehensive high temperature tolerance index two-year average of 4.9,the variety of full two excellent 681 is about 2.5,the variety of IR64 is 1.5,the species Mianhui 101 is 1.1.The variance analysis showed that the difference was not obvious between the years,and the difference between the varieties and the treatment temperature was extremely significant.Through the high temperature tolerance index and its corresponding strong inflection point,the corresponding high temperature tolerance index(heading flowering period,4-6 days):N22 is fully resistant to 35?(Daily average temperature of 31.8?),but not resistant to 37 ?(daily average temperature of 33.7 ?),Quanliangyou681 can withstand 33 ?(average daily temperature 29.8 ?),but not resistant to 35?(Daily average temperature of 31.8?),IR64 and Mianhui 101 were resistant to 33?(daily average temperature of 29.8?).2.The results showed that there was no significant difference in pollination rate between 35? and 37?,and the pollen germination rate of rice decreased by high temperature.The high temperature affected the pollination number and germination number of rice stigma,and the variety N22 was the best.The anthers had no significant change in the length of anthers in four rice cultivars.The high temperature had no obvious effect on the anthers cracking of the QuanLiangyou 681 and IR64.The high temperature treatment increased the length and width of the anthers of the cultivars N22,The peak length and base length of the cultivar Mianhui 101 were significantly different.There was no significant effect of high temperature on the base width of four varieties with different heat tolerance.3.The results showed that the tested rice resources were divided into three groups according to the screening results.Among them,the first category,16143 and Guanglu dwarf 15 comprehensive high temperature index were more than 5.0,belong to the extreme heat-resistant varieties;the second category,including varieties SDWG001,SDBN001 and SDSL013,the integrated high temperature index between 3.0 to 5.0,are strong heat-resistant varieties;the third category,including SDNR005 and SDXJ001,comprehensive high temperature index is less than 3.0,are generally heat-resistant varieties.4.Anther Proteomics analysis showed that there were 6(2 up-regulated,4 down-regulated)and 0 differential proteins in Mianhui 101 and N22 at 33?.At 35?,Mianhui 101 and N22 were 52(28 up-regulated,24 down-regulated)and 26(10 up-regulated,16 down-regulated)differential proteins,respectively.When the temperature rose to 37?,the differential expression proteins of Mianhui 101 and N22 were 81(36 up-regulated,45 down-regulated)and 129(48 up-regulated and 81 down-regulated)respectively;the differentially expressed proteins were mainly 15 Biological processes,10 cell compartment and 7 different molecular functions.In the biological process,there are three main categories of metabolic processes,cellular processes and single biological processes.The cell compartment mainly includes cells,organelles and macromolecular complexes.The three major functional groups mainly include catalytic activity,binding and structural activity.At 35? and 37?,N22 and Mianhui 101 have 14(3 up-regulated,11 down-regulated),21(10 up-regulated,11 down-regulated)specific HS response proteins.N22 of the three specific uptake proteins are stress-responsive proteins,of which 2 sHSPs,1 peroxidase.Mianhui 101 did not detect HSPs at 35 ° C and two HSPs were detected at 37?.N22 had 4 and 7 HSPs at 35? and 37?,respectively.Of the 21 specific HS response proteins,which were not dependent on temperature,10 were down-regulated.Nine of the 10 down-regulated proteins were ribosomal proteins.In summary,using the daily maximum temperature of 33?,35?,37? simulated thermal weather gradient high temperature can be more reasonable to identify the high temperature tolerance of rice varieties.The results showed that the cultivars had high sensitivity to different varieties and were stable during the year.The differences of varieties were clear and reasonable,and they could be used for the comparison of heat resistance between varieties.According to the variety of comprehensive high temperature tolerance index,researcher can also roughly determine the impact of inflection point temperature.Therefore,based on this experiment is expected to establish a stable,reliable and accurate rice varieties of high temperature tolerance identification of new methods.In addition,according to the pollination performance of the stigma and the anthers cracking at the high temperature,the physiological reason that the fertilization was affected at high temperature could be greater than the morphological reasons.African rice may be an important resource base for the world's high temperature tolerance.The small heat shock protein(sHSPs)may play an important role in the heat tolerance of rice.The expression of ribosomal protein at high temperature may be an important reason for susceptible varieties to sensitive to high temperature. |
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