title: 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.
authors.affiliation: Department of Genetics, Osmania University, Hyderabad 500 007, India.
authors.forename: P
authors.initials: P
authors.lastname: Surender Reddy
authors.affiliation: Department of Genetics, Osmania University, Hyderabad 500 007, India.
authors.forename: Gadi
authors.initials: G
authors.lastname: Jogeswar
authors.affiliation: Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500 047, India.
authors.forename: Girish K
authors.initials: GK
authors.lastname: Rasineni
authors.affiliation: Central Research Institute for Dryland Agriculture, Santoshnagar, Hyderabad 500 059, India.
authors.forename: M
authors.initials: M
authors.lastname: Maheswari
authors.affiliation: Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500 047, India.
authors.forename: Attipalli R
authors.initials: AR
authors.lastname: Reddy
authors.affiliation: International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru 502 324, India.
authors.forename: Rajeev K
authors.initials: RK
authors.lastname: Varshney
authors.affiliation: Department of Genetics, Osmania University, Hyderabad 500 007, India. Electronic address: pbkavi@yahoo.com.
authors.forename: P B
authors.initials: PB
authors.lastname: Kavi Kishor
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D009997:Osmotic Pressure; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D010788:Photosynthesis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*; D011392:Proline / Q000096:biosynthesis* / Q000235:genetics; D045868:Sorghum / Q000235:genetics / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D010940:Plant Proteins; D011392:Proline; D017853:Phosphotransferases (Alcohol Group Acceptor)
keywords: Antioxidant enzymes; Proline; Pyrroline-5-carboxylate synthetase gene; Salt stress; Sorghum bicolor (L.) Moench