Tomato plants ectopically expressing Arabidopsis CBF1 show enhanced resistance to water deficit stress

A DNA cassette containing an Arabidopsis C repeat/dehydration-responsive element binding factor 1 (CBF1) cDNA and a nos terminator, driven by a cauliflower mosaic virus 35S promoter, was transformed into the tomato (Lycopersicon esculentum) genome. These transgenic tomato plants were more resistant to water deficit stress than the wild-type plants. The transgenic plants exhibited growth retardation by showing dwarf phenotype, and the fruit and seed numbers and fresh weight of the transgenic tomato plants were apparently less than those of the wild-type plants. Exogenous gibberellic acid treatment reversed the growth retardation and enhanced growth of transgenic tomato plants, but did not affect the level of water deficit resistance. The stomata of the transgenic CBF1 tomato plants closed more rapidly than the wild type after water deficit treatment with or without gibberellic acid pretreatment. The transgenic tomato plants contained higher levels of Pro than those of the wild-type plants under normal or water deficit conditions. Subtractive hybridization was used to isolate the responsive genes to heterologous CBF1 in transgenic tomato plants and the CAT1 (CATALASE1) was characterized. Catalase activity increased, and hydrogen peroxide concentration decreased in transgenic tomato plants compared with the wild-type plants with or without water deficit stress. These results indicated that the heterologous Arabidopsis CBF1 can confer water deficit resistance in transgenic tomato plants.     

Expression of Arabidopsis CBF1 regulated by an ABA/stress inducible promoter in transgenic tomato confers stress tolerance without affecting yield

Modern‐day plants are subjected to various biotic and abiotic stresses thereby limiting plant productivity and quality. It has previously been reported that the use of a strong constitutive 35S cauliflower mosaic virus (CaMV) promoter to drive the expression of Arabidopsis CBF1 in tomato improved tolerance to cold, drought and salt loading, at the expense of growth and yield under normal growth conditions. Hence in the present study, the suitability of expressing the Arabidopsis CBF1 driven by three copies of an ABA‐responsive complex (ABRC1) from the barley HAV22 gene in order to improve the agronomic performance of the transgenic tomato plants was investigated. Northern blot analysis indicated that CBF1 gene expression was induced by chilling, water‐deficit and salt treatment in the transgenic tomato plants. Under these tested stress conditions, transgenic tomato plants exhibited enhanced tolerance to chilling, water‐deficit, and salt stress in comparison with untransformed plants. Under normal growing conditions the ABRC1‐CBF1 tomato plants maintained normal growth and yield similar to the untransformed plants. The results demonstrate the promise of using ABRC1‐CBF1 tomato plants in highly stressed conditions which will in turn benefit agriculture.     

拟南芥CBF1与植物对低温和干旱的抗性

对冷驯化过程中基因表达差异的认识,使抗冻基因(COR)的克隆及其功能的分析成为研究冷驯化过程的主要目标。在拟南芥和其他抗冻植物中,分离了许多COR基因,这些基因对植物抗冻起着非常重要的作用。在拟南芥COR调控的研究中,发现了CBF转录因子的基因家族,其中CBF1能调控一组COR基因的表达。近年来,在冷敏植物如番茄和玉米中也发现了CBF类似基因,拟南芥CBF1基因在转基因番茄中的过量表达提高了植株的抗寒和抗旱性。这一研究结果展示了拟南芥CBF1类似基因的应用可能为冷敏植物抗寒和抗旱性的品种改良提供一条新的途径。     

Expression of a sweet cherry DREB1/CBF ortholog in Arabidopsis confers salt and freezing tolerance

Dehydration responsive element binding protein 1 (DREB1)/C-repeat binding factor (CBF) induces the expression of many stress-inducible genes in Arabidopsis. We have previously reported the identification of three DREB1/ICBF homologs from sweet cherry (Prunus avium). To identify the function of these homologs, one of the genes, CIG-B, was transformed into Arabidopsis. In one of the transgenic plant lines, the DREB1/CBF target gene cor15a was induced in the absence of stress treatment. The cor15a-overexpressing transgenic plant exhibited mild growth retardation and had greater salt and freezing tolerance than did the wild-type and the transgenic lines in which cor15a was not induced. These results suggest that this sweet cherry DREB1/CBF homolog has a function similar to that of DREB1/CBF.     

Arabidopsis CBF3/DREB1A and ABF3 in transgenic rice increased tolerance to abiotic stress without stunting growth

Rice (Oryza sativa), a monocotyledonous plant that does not cold acclimate, has evolved differently from Arabidopsis (Arabidopsis thaliana), which cold acclimates. To understand the stress response of rice in comparison with that of Arabidopsis, we developed transgenic rice plants that constitutively expressed CBF3/DREB1A (CBF3) and ABF3, Arabidopsis genes that function in abscisic acid-independent and abscisic acid-dependent stress-response pathways, respectively. CBF3 in transgenic rice elevated tolerance to drought and high salinity, and produced relatively low levels of tolerance to low-temperature exposure. These data were in direct contrast to CBF3 in Arabidopsis, which is known to function primarily to enhance freezing tolerance. ABF3 in transgenic rice increased tolerance to drought stress alone. By using the 60 K Rice Whole Genome Microarray and RNA gel-blot analyses, we identified 12 and 7 target genes that were activated in transgenic rice plants by CBF3 and ABF3, respectively, which appear to render the corresponding plants acclimated for stress conditions. The target genes together with 13 and 27 additional genes are induced further upon exposure to drought stress, consequently making the transgenic plants more tolerant to stress conditions. Interestingly, our transgenic plants exhibited neither growth inhibition nor visible phenotypic alterations despite constitutive expression of the CBF3 or ABF3, unlike the results previously obtained from Arabidopsis where transgenic plants were stunted.     

组成型表达的ClpB基因提高番茄植株的耐冷性

用农杆菌介导法将CaMV35S启动子驱动的ClpB cDNA导入番茄,并比较了转基因和未转基因番茄的抗冷能力。当受冷胁迫后,转基因番茄比未转基因番茄表现出较轻的冷胁迫症状,并维持较高的PSII水平。     

拟南芥非生物胁迫应答基因表达的调节子研究概况

分子生物学研究表明,植物中由诸如干旱、高盐和低温等环境胁迫因子诱导的几个基因具有多种功能。大多数干旱应答基因是由植物激素脱落酸（ABA）诱导的,但也有少数基因例外。对模式植物拟南芥基因表达中的干旱应答基因的分析表明,至少存在4个独立调节系统（调节子）。对典型胁迫诱导表达的一些基因中启动子的顺势作用元件和影响这些基因表达的转录子也已进行了分析。已经分离出与脱水效应元件/C重复序列（DRE/CRT）顺势作用元件结合的转录因子,并命名为DRE结合蛋白1/C重复序列结合因子（DREB1/CBF）和DRE结合蛋白2（DREB2）。在转基因拟南芥植株中,DREB1/CBF过量表达可增加其抗寒、抗旱和抗盐碱的能力。DREB1/CBF基因已成功地在许多不同作物中得到应用,从而提高作物对非生物胁迫的耐受性。与胁迫反应相关的其他转录因子的研究也正在取得进展。