PDF(Pubmed)
Abstract：
BACKGROUND: Development of transgenic rice overexpressing transcription factors involved in drought response has been previously reported to confer drought tolerance and therefore represents a means of crop improvement. We transformed lowland rice IR64 with OsTZF5, encoding a CCCH-tandem zinc finger protein, under the control of the rice LIP9 stress-inducible promoter and compared the drought response of transgenic lines and nulls to IR64 in successive screenhouse paddy and field trials up to the T6 generation.
RESULTS: Compared to the well-watered conditions, the level of drought stress across experiments varied from a minimum of - 25 to - 75 kPa at a soil depth of 30 cm which reduced biomass by 30-55% and grain yield by 1-92%, presenting a range of drought severities. OsTZF5 transgenic lines showed high yield advantage under drought over IR64 in early generations, which was related to shorter time to flowering, lower shoot biomass and higher harvest index. However, the increases in values for yield and related traits in the transgenics became smaller over successive generations despite continued detection of drought-induced transgene expression as conferred by the LIP9 promoter. The decreased advantage of the transgenics over generations tended to coincide with increased levels of homozygosity. Background cleaning of the transgenic lines as well as introgression of the transgene into an IR64 line containing major-effect drought yield QTLs, which were evaluated starting at the BC3F1 and BC2F3 generation, respectively, did not result in consistently increased yield under drought as compared to the respective checks.
CONCLUSIONS: Although we cannot conclusively explain the genetic factors behind the loss of yield advantage of the transgenics under drought across generations, our results help in distinguishing among potential drought tolerance mechanisms related to effectiveness of the transgenics, since early flowering and harvest index most closely reflected the levels of yield advantage in the transgenics across generations while reduced biomass did not.
RESULTS: Compared to the well-watered conditions, the level of drought stress across experiments varied from a minimum of - 25 to - 75 kPa at a soil depth of 30 cm which reduced biomass by 30-55% and grain yield by 1-92%, presenting a range of drought severities. OsTZF5 transgenic lines showed high yield advantage under drought over IR64 in early generations, which was related to shorter time to flowering, lower shoot biomass and higher harvest index. However, the increases in values for yield and related traits in the transgenics became smaller over successive generations despite continued detection of drought-induced transgene expression as conferred by the LIP9 promoter. The decreased advantage of the transgenics over generations tended to coincide with increased levels of homozygosity. Background cleaning of the transgenic lines as well as introgression of the transgene into an IR64 line containing major-effect drought yield QTLs, which were evaluated starting at the BC3F1 and BC2F3 generation, respectively, did not result in consistently increased yield under drought as compared to the respective checks.
CONCLUSIONS: Although we cannot conclusively explain the genetic factors behind the loss of yield advantage of the transgenics under drought across generations, our results help in distinguishing among potential drought tolerance mechanisms related to effectiveness of the transgenics, since early flowering and harvest index most closely reflected the levels of yield advantage in the transgenics across generations while reduced biomass did not.
摘要：
背景:先前已经报道过表达与干旱响应有关的转录因子的转基因水稻的开发赋予干旱耐受性,因此代表了作物改良的手段。我们用编码CCCH串联锌指蛋白的OsTZF5转化了低地水稻IR64，在水稻LIP9胁迫诱导型启动子的控制下，并比较了转基因品系和Nulls在连续的温室稻田和田间试验中对IR64的干旱响应直到T6代。
结果：与充分浇水条件相比，在30厘米的土壤深度下，整个实验的干旱胁迫水平从最低-25到-75kPa不等，这将生物量降低了30-55％，谷物产量降低了1-92％，呈现一系列干旱严重程度。OsTZF5转基因株系在干旱条件下比早期的IR64表现出高产优势，这与开花时间更短有关，较低的芽生物量和较高的收获指数。然而,尽管持续检测到LIP9启动子赋予的干旱诱导的转基因表达，但转基因中产量和相关性状值的增加在连续世代中变得更小。在世代中，转基因优势的降低倾向于与纯合性水平的提高相吻合。转基因品系的背景清洁以及转基因渗入含有主要影响干旱产量QTL的IR64品系，从BC3F1和BC2F3一代开始进行评估，分别,与各自的检查相比，在干旱下并没有导致产量持续增加。
结论：尽管我们无法最终解释干旱下转基因作物产量优势丧失的遗传因素，我们的结果有助于区分与转基因有效性相关的潜在干旱耐受机制，因为早期开花和收获指数最密切地反映了跨代转基因的产量优势水平，而减少的生物量却没有。
结果：与充分浇水条件相比，在30厘米的土壤深度下，整个实验的干旱胁迫水平从最低-25到-75kPa不等，这将生物量降低了30-55％，谷物产量降低了1-92％，呈现一系列干旱严重程度。OsTZF5转基因株系在干旱条件下比早期的IR64表现出高产优势，这与开花时间更短有关，较低的芽生物量和较高的收获指数。然而,尽管持续检测到LIP9启动子赋予的干旱诱导的转基因表达，但转基因中产量和相关性状值的增加在连续世代中变得更小。在世代中，转基因优势的降低倾向于与纯合性水平的提高相吻合。转基因品系的背景清洁以及转基因渗入含有主要影响干旱产量QTL的IR64品系，从BC3F1和BC2F3一代开始进行评估，分别,与各自的检查相比，在干旱下并没有导致产量持续增加。
结论：尽管我们无法最终解释干旱下转基因作物产量优势丧失的遗传因素，我们的结果有助于区分与转基因有效性相关的潜在干旱耐受机制，因为早期开花和收获指数最密切地反映了跨代转基因的产量优势水平，而减少的生物量却没有。
