Stress Inducible Expression of AtDREB1A Transcription Factor in Transgenic Peanut (Arachis hypogaea L.) Conferred Tolerance to Soil-Moisture Deficit Stress

Abstract

Peanut, an important oilseed crop, is gaining priority for the development of drought tolerant genotypes in recent times, since the area under drought is constantly on the rise. To achieve this, one of the important strategies is to genetically engineer the ruling peanut varieties using transcription factor regulating the expression of several downstream, abiotic-stress responsive gene(s). In this study, eight independent transgenic peanut (cv. GG20) lines were developed using AtDREB1A gene, encoding for a transcription factor, through Agrobacterium-mediated genetic transformation. The transgene insertion was confirmed in (T 0 ) using PCR and Dot-blot analysis, while copy-number(s) was ascertained using Southern-blot analysis. The inheritance of AtDREB1A gene in individual transgenic plants (T 1 and T 2 ) was confirmed using PCR. In homozygous transgenic plants (T 2 ), under soil-moisture deficit stress, elevated level of AtDREB1A transgene expression was observed by RT-PCR assay. The transgenic plants at 45-d or reproductive growth stage showed tolerance to severe soil-moisture deficit stress. Physio-biochemical parameters such as proline content, osmotic potential, relative water content, electrolytic leakage, and total-chlorophyll content were found positively correlated with growth-related traits without any morphological abnormality, when compared to wild-type. qPCR analysis revealed consistent increase in expression of AtDREB1A gene under progressive soil-moisture deficit stress in two homozygous transgenic plants. The transgene expression showed significant correlation with improved physio-biochemical traits. The improvement of drought-stress tolerance in combination with improved growth-related traits is very essential criterion for a premium peanut cultivar like GG20, so that marginal farmers of India can incur the economic benefits during seasonal drought and water scarcity.

Expression of Pennisetum glaucum Eukaryotic Translational Initiation Factor 4A (PgeIF4A) Confers Improved Drought, Salinity, and Oxidative Stress Tolerance in Groundnut

“…It could be due to the positive regulation of rd29A promoter which involved in stress inducible expression of transgene. Similarly, higher expression of AtDREB1A was seen in groundnut transgenic plants which were regulated by rd29A promoter (Sarkar et al, 2014, 2016). It indicated that there was positive correlation between regulation of transgene and stress tolerance.…”

“…The expression of OsDREB2A under the regulation of rd29A promoter conferred drought and salinity tolerance and minimized the negative growth effects under stress and non-stress condition in rice (Mallikarjuna et al, 2011). However, constitutively expressing AtDREB1A groundnut plants showed stunted growth and phenotypic abnormality when compared with those transgenics with the same gene under rd29A inducible expression (Bhatnagar-Mathur et al, 2007; Sarkar et al, 2016). Similarly, constitutive over expression of AtDREB1A gene caused growth retardation in transgenic Arabidopsis plants (Kasuga et al, 1999).…”

“…Since the root system developed strongly, access to the uptake of nutrients could be increased in the plants. DREB1A expressing groundnut plants had better access of water uptake since the root system penetrated into deeper soil which resulted in significant tolerance under limited moisture conditions (Bhatnagar-Mathur et al, 2014; Sarkar et al, 2016). …”

“…The genes from Salicornia brachiata, ascorbate peroxidase ( SbAPX ), and abscisic acid stress ripening ( SbASR ) genes when expressed in groundnut displayed salt and drought stress tolerance coupled with more chlorophyll retention and enhanced levels of relative water content under normal/stress conditions (Singh et al, 2014; Tiwari et al, 2015). The transcription factors from Arabidopsis, AtNAC2 (Patil et al, 2014), AtDREB1A (Sarkar et al, 2014, 2016) and horsegram, MuNAC4 (Pandurangaiah et al, 2014) were exhibited drought and salt stress tolerance in groundnut by reducing the membrane damage and improving scavenging of reactive oxygen species scavenging (ROS). Groundnut transgenic plants ( cv TMV-2) simultaneously expressing three TFs ( AtDREB2A, AtHB7 , and AtABF3 ) displayed to increase drought, salinity, and oxidative stress tolerance compared to wild type (Pruthvi et al, 2014).…”

“…However, positive growth regulation was seen in rd29A:AtDREB1A expressing plants and thereby improved 40% transpiration efficiency under limited water conditions (Bhatnagar-Mathur et al, 2014). Thus, expression of the stress related genes under the regulation of stress inducible promoters could be more rewarding rather than constitutive expression to minimize negative effects on plant growth performance (Sarkar et al, 2016). …”