Improvement of stress tolerance of wheat and barley by modulation of expression of DREB/CBF factors

Abstract

SummaryTranscription factors have been shown to control the activity of multiple stress response genes in a coordinated manner and therefore represent attractive targets for application in molecular plant breeding. We investigated the possibility of modulating the transcriptional regulation of drought and cold responses in the agriculturally important species, wheat and barley, with a view to increase drought and frost tolerance. Transgenic wheat and barley plants were generated showing constitutive (double 35S) and drought-inducible (maize Rab17) expression of the TaDREB2 and TaDREB3 transcription factors isolated from wheat grain. Transgenic populations with constitutive over-expression showed slower growth, delayed flowering and lower grain yields relative to the nontransgenic controls. However, both the TaDREB2 and TaDREB3 transgenic plants showed improved survival under severe drought conditions relative to nontransgenic controls. There were two components to the drought tolerance: real (activation of drought-stress-inducible genes) and 'seeming' (consumption of less water as a result of smaller size and ⁄ or slower growth of transgenics compared to controls). The undesired changes in plant development associated with the 'seeming' component of tolerance could be alleviated by using a drought-inducible promoter. In addition to drought tolerance, both TaDREB2 and TaDREB3 transgenic plants with constitutive over-expression of the transgene showed a significant improvement in frost tolerance. The increased expression of TaDREB2 and TaDREB3 lead to elevated expression in the transgenics of 10 other CBF ⁄ DREB genes and a large number of stress responsive LEA ⁄ COR ⁄ DHN genes known to be responsible for the protection of cell from damage and desiccation under stress.

Identification and freedom to operate analysis of potential genes for drought tolerance in maize

“…This suggests that ZmDREB2A and GmDREB2 do not require modification (Yang et al, 2010). Barley plants transformed independently with TaDREB3 and TaDREB2 and evaluated for drought and frost tolerance showed similar results (Morran et al, 2011). A transgenic population constitutively overexpressing these factors showed slow growth, a delay in flowering and less grain yield than their untransformed counterparts.…”

“…This study also evaluated the expression of TaDREB2 and TaDREB3 in well-hydrated plants and under different types of stress. Under no biotic stress, their expression was low, while they were highly induced by drought, especially TaDREB2; cold conditions only activated them weakly; TaDREB2 was strongly activated in seeds by mechanical damage; no activation was detected by saline stress; and TaDREB3 was weakly induced in leaves by ABA (Morran et al, 2011). Taking all these results into account, TaDREB2 was chosen for the design of an expression cassette using the drought-inducible promoter rab17 (Al-Abed et al, 2007) to avoid the deleterious effects described by Wang et al (2003).…”

Yield stability for cereals in a changing climate

“…Likely candidate genes for the improvement of reproductive stage abiotic stress tolerance are CBF/DREB1 transcription factors that are affected by cold and drought stress. Overexpression of CBF/DREB1 transcription factors under control of a strong constitutive promoter improves stress tolerance, but they lead to stunted growth and there is an adverse effect on yield (Oh et al 2007;Morran et al 2011). The use of an inducible promoter such as the drought-inducible rd29A promoter was shown to overcome the negative effect of DREB1A overexpression (Kasuga et al 2004;Pellegrineschi et al 2004).…”

Diseño de casetes de expresión que confieran tolerancia a sequía y a glufosinato en maíz (Zea mays)

“…Fueron seleccionados tres genes denominados TaDREB3 AP2 (Lopato et al, 2006;Morran et al, 2011), AtZAT10 (Meissner y Michael,1997;Mittler et al, 2006) y CspB (Willimsky et al, 1992;Castiglioni et al, 2008), que pueden conferir tolerancia a sequía.…”

“…Seis factores de transcripción DREB que incluyen cuatro genes DREB1/CBF y dos genes DREB2 fueron identificados en Arabidopsis. La expresión de DREB1/CBFs es inducida por sequía, sal y frio, mientras que la expresión de DREB2 es únicamente inducida por sequía y sal (Liu et al, 1998;Sakuma et al, 2006b;Morran et al, 2011). Diferentes estudios han informado mejora en la tolerancia a sequía mediante transformación genética en plantas cultivadas con tales factores de transcripción, en tomate (Solanum lycopersicum) (Hsieh et al, 2002), trigo (Triticum aestivum) (Pellegrineschi et al, 2004;XiaoYan et al, 2005;Wang et al, 2006), maíz (Al-Abed et al, 2007;Zhang et al, 2010) y arroz (Oriza sativa) (Oh et al, 2005;Oh et al, 2007;Chen et al, 2008;Xiao et al, 2009); sin embargo, uno de los principales inconvenientes en transformación genética de plantas con DREB/CBF han sido los defectos en el crecimiento cuando se expresa constitutivamente, lo cual se ha minimizado mediante el uso de promotores inducibles por estrés.…”