Effect of Heat Stress on Grain Growth, Starch Synthesis and Protein Synthesis in Grains of Wheat (Triticum aestivum L.) Varieties Differing in Grain Weight Stability

The effect of heat stress on the components of grain weight was analysed in wheat ( Triticum aestivum L.) varieties differing in grain weight stability. The wheat varieties PBW154, Sonalika and Hindi62 were raised in the field (New Delhi, India; 77°12' E, 28°40' N, 228.6 m a.s.l.) at three dates of sowing: 19 November 1992 (DOS I), 14 December 1992 (DOS II) and 18 January 1993 (DOS III). The late-sown crop (DOS III) experienced 6–8 °C warmer temperatures during grain development than the crop sown at the normal time (DOS I). The heat susceptibility index (S) revealed that grain weight was less susceptible to heat in Sonalika and PBW154 than in Hindi62. Heat stress reduced both the grain growth duration (GGD) and the grain growth rate (GGR). The grain weight reduction in PBW154 and Sonalika was mainly due to a reduction in GGR, while that of Hindi62 was due to a reduction in GGD. In vivo studies on starch and protein synthesis in excised endosperm at 15, 25 and 35 °C revealed that both processes were more thermotolerant in Hindi62 than in PBW154. The grain starch content was stable in Hindi62 while that in PBW154 was significantly reduced under heat stress. The grain nitrogen content at maturity increased in both varieties under heat stress. It was concluded that the heat susceptibility of grain weight in Hindi62 was mainly due to a reduction in GGD, although GGR, starch and protein synthesis were more thermotolerant in developing grains of Hindi62 than in those of PBW154.     

Induced thermotolerance and expression of heat shock protein 70 in sea cucumber <Emphasis Type="Italic">Apostichopus japonicus</Emphasis>

ABSTRACT:   Thermal limits, induced thermotolerance and the expression of heat shock protein 70 (Hsp70) in an echinoderm Apostichopus japonicus were studied. The sublethal and lethal temperatures for the juveniles were 30 and 34°C, respectively; a previous sublethal heat shock exposure (30°C, 2 h) could increase the survival rates of the sea cucumbers when they were exposed to 34°C. This induced thermotolerance could last for at least 2 days. Levels of Hsp70 increased substantially after sublethal heat shock exposure and linearly decreased with time. This result indicated that a close relationship existed between the induction of thermotolerance and the levels of Hsp70 in A. japonicus.     

早期热习服对肉鸡耐热力发育的影响研究进展

从早期热习服的概念、耐热力的评价指标以及早期热习服的时机出发,总结与分析了早期热习服对肉鸡后期耐热力形成的影响规律,试图探索出早期热习服提高肉鸡后期耐热力的机理。     

Characterization and taxonomic reassessment of the box blight pathogen Calonectria pseudonaviculata,introducing Calonectria henricotiae sp. nov.

Calonectria pseudonaviculata, the causal agent of the disease of Buxus spp. known as ‘box blight’, was first detected in the mid‐1990s in the UK and New Zealand. Since then, the geographic range of box blight has rapidly expanded to at least 21 countries throughout temperate regions of the world, causing significant losses in nurseries, gardens and wild boxwood populations. This study determined the genetic diversity in a collection of 234 Calonectria isolates from diseased Buxus plants, originating from 15 countries and four continents. Two genetic clades, G1 and G2, were identified within this sample using multilocus phylogenetic analysis. The application of genealogical concordance phylogenetic species recognition criteria using four independent nuclear loci determined that the Calonectria isolates in these two clades are separate phylogenetic species. The isolates in the G1 clade were upheld as C. pseudonaviculata sensu stricto. Based on phylogenetic distinctiveness and the lack of mating, a new species is proposed, Calonectria henricotiae sp. nov., for the Calonectria isolates in the G2 clade. A PCR‐RFLP assay and real‐time PCR assays were developed to easily and reproducibly differentiate these species. To assess the practical implications of the identification of the two species, their physiology, fungicide susceptibility and pathogenicity were compared. No differences in pathogenicity were observed. However, C. henricotiae isolates exhibited greater thermotolerance and reduced sensitivity to specific triazole as well as strobilurin fungicides. The identification of a second phylogenetic species causing box blight may have a substantial impact on the epidemiology and control of this destructive disease.     

紫花苜蓿MsMBF 1c基因在拟南芥中 表达提高转基因植株的耐热性

高温能危害植物的生长发育,是限制紫花苜蓿在南方地区推广的主要非生物胁迫因素之一。从“中苜1号”紫花苜蓿品种克隆获得紫花苜蓿多桥蛋白1c(Medicago sativa Multi protein Bridging Factors 1c, MsMBF1c)全长编码序列,发现紫花苜蓿MsMBF1c蛋白与拟南芥AtMBF1c蛋白同源相似性高达72%。分析MsMBF1c在根、茎、叶、花和果实等不同组织中,以及在高温、干旱以及高温和干旱组合胁迫条件下的表达模式,发现该基因在不同组织中的表达强度依次为花>根>叶>茎>果实;MsMBF1c显著受高温、干旱以及高温和干旱组合诱导,分别被上调4.21、2.15和4.59倍。构建pBI121-35S: MsMBF1c过量表达载体并转入模式植物拟南芥(wild type, WT),在T₃代获得卡那抗性不分离的过量表达株系(over expression, OE);利用OE与Atmbf1c突变体(mutant, MUT)杂交的方法获得互补株系(complementary, COM),并通过PCR与qRT-PCR的方法进行分子和表达验证。平行比较OE、COM、MUT以及WT等不同拟南芥株系在高温胁迫后的种子发芽率和幼苗存活率,在正常情况下,OE、COM、MUT以及WT拟南芥株系种子的发芽率没有显著差异(97.6%~100.0%),高温胁迫后,WT发芽率下降到71.7%,MUT发芽率下降到66.0%,显著低于WT(P<0.05);而COM与3个独立的OE株系的发芽率达79.3%~87.0%,显著高于WT(P<0.05)。在幼苗耐热试验中,OE、COM、MUT以及WT株系的存活率在正常条件下差异不显著,高温胁迫后,WT幼苗存活率下降到16.7%,MUT下降到10.0%,显著低于WT(P<0.05);而COM与3个独立的OE株系存活率下降到40.0%~76.7%,显著高于WT(P<0.05)。利用real-time PCR方法,分析HSFA1a、HSFA2、HSFA3、HSFB1、WRKY25、WRKY18、DREB2a等耐热调节关键基因在OE、MUT和WT拟南芥株系的相对表达情况,在正常条件下,HSFA2、WRKY18与DREB2a在MUT株系中的表达显著低于WT(0.33~0.47)。而在OE株系中,除HSFA1a外,HSFA2、HSFA3、HSFB1、WRKY25、WRKY18、DREB2a的表达相对WT株系都有不同程度上调,幅度为1.74~3.80。高温胁迫后,与WT相比,HSFA2、HSFA3、HSFB1、WRKY18与DREB2a在MUT株系中的表达中被显著下调,在OE株系中,只有WRKY18显著高于WT外,其余基因的表达在OE与WT株系中差异不显著。综合分析,MsMBF1c是一个功能比较保守的耐热调节基因,过量表达MsMBF1c能够互补拟南芥mbf1c突变体耐热缺失表型,并能够增强拟南芥在种子萌发与幼苗生长阶段的耐热性。MsMBF1c可能与AtMBF1c一样,与其他耐热调节关键基因互作调节植物耐热性。     

The induction of Hsp70 synthesis by non‐lethal heat shock confers thermotolerance and resistance to lethal ammonia stress in the common carp,Cyprinus carpio (Linn)

Exposure to heat‐shock protein (Hsp) stimulating factors induces Hsp accumulation and confers tolerance to lethal ammonia stress on the common carp Cyprinus carpio. This study investigated whether a non‐lethal heat shock bestowed similar protective effects against ammonia and induced thermotolerance, both thought to be rendered by increased amounts of Hsps. The 30‐min lethal temperature (30 min LHT) and 1‐h lethal ammonia concentration (1 h LCT) for this species occurred at 41°C and 14.2 mg/L NH₃ respectively. Heating juvenile carp (5 cm) from 28°C to 32, 34 and 38°C, with a subsequent 8‐h recovery period augmented tolerance to lethal heat and ammonia perturbation by two to threefold as compared with animals held at 28°C. Protection occurred in conjunction with Hsp70 accumulation in gills, substantiating the role of this Hsp in enhancing the stress tolerance of common carp.     

高温胁迫下2,4-表油菜素内酯对浙贝母花期耐热性及光合特性的影响

在盆栽条件下,以狭叶浙贝母(Fritillaria thunbergii Miq.)为材料,研究了浙贝母花期高温胁迫条件下表油菜素内酯(EBR)对浙贝母耐热性和光合特性的影响。结果表明,0.10、0.50 mg/L EBR能明显提高叶片中可溶性蛋白含量、SOD、POD和CAT活性,降低MDA含量,增强其抗氧化能力,缓解高温胁迫导致的膜质过氧化伤害;同时,EBR提高了叶片叶绿素含量、Pn、Gs和Tr,从而提高了高温胁迫下浙贝母植株的光合作用;然而EBR并不能提高其Pro及可溶性糖含量,对叶片中类胡萝卜素及胞间CO2浓度(Ci)影响差异不大。结果表明,EBR通过提高高温胁迫下浙贝母叶片可溶性蛋白及叶绿素含量、抗氧化酶活性,来降低体内活性氧水平,维持较高的光合速率,以0.50 mg/L EBR效果最好。