Transgenic peanut overexpressing mtlD gene confers enhanced salinity stress tolerance via mannitol accumulation and differential antioxidative responses

Abstract

Globally, peanut is an important oilseed crop, which is cultivated under different agro-climatic zones. Soil salinity is one of the major constraints in peanut cultivation. Therefore, to understand the physio-biochemical mechanisms imparting salinity stress, four transgenic peanut lines (cv. GG20) already developed and confirmed by our lab, having bacterial mannitol dehydrogenase gene (mtlD), were subjected to different levels of salinity stresses (1, 2 and 3 dS m -1 ) in pots under containment facility. Further, these lines were also characterized for various physio-biochemical parameters at flowering, pegging and pod formation stages. All the transgenic lines recorded significantly higher mannitol dehydrogenase (MTD) activity and mannitol accumulation than the wild type (WT). Under salinity stress, significantly higher levels of superoxide dismutase, catalase, guaiacol peroxidase, ascorbate peroxidase, glutathione reductase activities, while significantly lower levels of H 2 O 2 and malondialdehyde contents, were recorded in the transgenics compared to WT. Similarly, significantly higher ascorbic acid and relative water content (RWC) were recorded in transgenic lines. The MTD activity showed positive correlation with various antioxidant enzymes, growth parameters and RWC, while negative correlation was recorded with H 2 O 2 and malondialdehyde content at most of the plant growth stages. The mtlD transgenic peanut lines under pot conditions were found maintaining lower oxidative injuries, indicating amelioration of salinity-induced oxidative stress by enhanced protection mechanisms via mannitol accumulation and antioxidative responses. The best lines identified (MTD1 and MTD4) may be used further as prebreeding source for imparting salinity stress tolerance in peanut. Besides, these lines may also be tested under openfield trials for release as salt-tolerant variety.

Osmoprotection in plants under abiotic stresses: new insights into a classical phenomenon

“…Rahnama et al (2011) reported improved salinity tolerance in transgenic potato expressing the mtlD gene, resulting over-accumulation of mannitol. Similarly, Patel et al (2016) reported enhanced salinity stress tolerance in transgenic peanut manipulated with bacterial mannitol dehydrogenase mtlD gene. Thus, incorporation of mannitol biosynthesis genes from different organisms into crop plants to enhance their tolerance to abiotic stresses can be an effective strategy to counter the adverse impacts of climate change.…”

Peanut (Arachis hypogaea L.): A Prospective Legume Crop to Offer Multiple Health Benefits Under Changing Climate

“…At present, China, India, the USA, and Argentina are the most notable peanut exporters. Peanut has become one of the major global oil‐seed crops cultivated on approximately 26 million ha in about 120 countries yielding about 35 to 40 million tons of peanut pods annually (FAO, ; Patel, Mandaliya, Mishra, Dobaria, & Thankappan, ; Sarkar et al., ). According to FAO, world production is above 45 million tons, averaging about 1.8 t/ha.…”

“…Similarly, the overexpression of AtDREB1A gene conferred salt tolerance in peanut through improved transpiration efficiency and growth which contributed to improved yield (Bhatnagar‐Mathur et al., ; Sarkar et al., ; Vadez, Rao, Bhatnagar‐Mathur, & Sharma, ). Apart from AtDREB1A gene, researchers investigated transgenic peanut plants expressing bacterial mannitol dehydrogenase ( mtlD ) gene (Hema et al., ; Nguyen et al., ; Patel et al., ). Another important gene that is targeted in transgenic peanut plants for inducing salt tolerance is AtNHX1 .…”

Transgenic Peanut (Arachis hypogaea L.) Overexpressing mtlD Gene Showed Improved Photosynthetic, Physio-Biochemical, and Yield-Parameters under Soil-Moisture Deficit Stress in Lysimeter System

“…The adverse effect of DS on plants begins with a decrease in the transpiration rate (TR) and stomatal conductance (SC) and consequently leaf water potential (WP), resulting in overall imbalance in water relationships and the photosynthetic rate (Pn) (Farooq et al, 2009 ; Krasensky and Jonak, 2012 ; Ashraf and Harris, 2013 ; Osakabe et al, 2014 ). These effects are followed by a reduction in the turgor pressure, transpiration, and relative water content (RWC) and often the formation of reactive oxygen species (ROS), resulting in an increase in malondialdehyde (MDA) content and ultimately poor yield (Farooq et al, 2009 ; Akcay et al, 2010 ; Patel et al, 2016 ).…”

“…Under DS conditions, plants also undergo various molecular changes, resulting in increased expression of stress-associated genes responsible for synthesizing various regulatory proteins, detoxifying enzymes, proline, and compatible solutes (Chaves et al, 2009 ; Osakabe et al, 2014 ). Compatible solutes such as, polyols, betaines, sugars, and amino acids can stabilize macromolecules and cellular structures, maintain the turgor pressure in cells through osmotic adjustments and re-establish the cellular redox balance by scavenging free radicals (Krasensky and Jonak, 2012 ; Patel et al, 2016 ).…”