Proline over-accumulation alleviates salt stress and protects photosynthetic and antioxidant enzyme activities in transgenic sorghum [Sorghum bicolor (L.) Moench]

Abstract

Shoot-tip derived callus cultures of Sorghum bicolor were transformed by Agrobacterium tumefaciens as well as by bombardment methods with the mutated pyrroline-5-carboxylate synthetase (P5CSF129A) gene encoding the key enzyme for proline biosynthesis from glutamate. The transgenics were selfed for three generations and T4 plants were examined for 100 mM NaCl stress tolerance in pot conditions. The effect of salt stress on chlorophyll and carotenoid contents, photosynthetic rate, stomatal conductance, internal carbon dioxide concentration, transpiration rates, intrinsic transpiration and water use efficiencies, proline content, MDA levels, and antioxidant enzyme activities were evaluated in 40-day-old transgenic lines and the results were compared with untransformed control plants. The results show that chlorophyll content declines by 65% in untransformed controls compared to 30-38% loss (significant at P < 0.05) in transgenics but not carotenoid levels. Photosynthetic rate (PSII activity) was reduced in untransformed controls almost completely, while it declined by 62-88% in different transgenic lines. Salinity induced ca 100% stomatal closure in untransformed plants, while stomatal conductance was decreased only by 64-81% in transgenics after 4 days. The intercellular CO2 decreased by ca 30% in individual transgenic lines. Malondialdehyde (MDA) content was lower in transgenics compared to untransformed controls. The activities of superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6) and glutathione reductase (GR; EC1.8.1.7) were quantified in leaves exposed to 100 mM NaCl stress and found higher in transgenics. The results suggest that transgenic lines were able to cope better with salt stress than untransformed controls by protecting photosynthetic and antioxidant enzyme activities.

Banana NAC transcription factor MusaNAC042 is positively associated with drought and salinity tolerance

“…However, such retardation was not observed in case of MusaNAC042 indicating that MusaNAC042 can be useful for increasing salinity and drought tolerance of banana. Abiotic stress conditions generally lead to proline accumulation (Surender Reddy et al 2015) which is known to act as molecular chaperon preventing protein denaturation along with maintaining osmotic balance (Székely et al 2007). Similarly in our study, transgenic banana lines overexpressing MusaNAC042 contained higher proline level after salinity and drought stress indicating that elevated proline can be one of the possibilities for enhanced stress tolerance of transgenic lines.…”

Overexpression of a Plasma Membrane Bound Na+/H+ Antiporter-Like Protein (SbNHXLP) Confers Salt Tolerance and Improves Fruit Yield in Tomato by Maintaining Ion Homeostasis

“…High proline accumulating lines of niger ( Guizotia abyssinica ) displayed significantly higher antioxidant enzyme activities compared to the lines that accumulate low levels (Sarvesh et al, 1996). Proline protected antioxidative enzyme activities in transgenic sorghum plants under NaCl stress (Reddy et al, 2015). Transgenics displayed reduced photochemical PSII activity compared to WT under salt stress, indicating less chlorophyll damage in transgenics.…”

“…Redondo-Gómez et al (2007) noticed a decline in stomatal conductance resulting in reduced photosynthetic rate. But, SbNHXLP transgenics displayed higher Fv/Fm ratio leading to better survival under salt stress like in transgenic sorghum (Reddy et al, 2015). Thus, SbNHXLP appears to be protecting photosynthetic as well as antioxidative enzyme activities.…”

Salt tolerance conferred by expression of a global regulator IrrE from Deinococcus radiodurans in oilseed rape

“…Under salt stress, ion imbalance and hyperosmotic stress also make the membranes vulnerable, so membrane damage is commonly used as an index to measure the salt tolerance. The malondialdehyde (MDA) level, a product of lipid peroxidation in biomembranes (Heath and Packer 1968), is considered a useful index to measure the extent of membrane injury and commonly known as an indicator of oxidative stress (Surender et al 2015). Salt often leads to oxidative stress in plants, and reactive oxygen species (ROS) generated as a result of oxidative stress are highly deleterious for plants (Ahmad et al 2012).…”