Modulation of ascorbate-glutathione cycle by selenate and sulphate treatments in the seedlings of two rice (Oryza sativa L.) cultivars

The trace element Selenium (Se) has a dual role in the growth and metabolism of plants. Low concentration of selenium (2 ?M selenate) promotes growth and counteracts the detrimental effects of abiotic stress as opposed to higher levels (?10 ?M) where it acts as a pro-oxidant. We focused on both individual and interactive influence of selenate and sulphate on thiol metabolism in seedlings of rice cultivars, satabdi and khitish. Inhibition of ascorbate contents by about 17% on an average, in the test seedlings treated with Se correlated with increased activities of ascorbate peroxidase and ascorbate oxidase in the cultivars. The glutathione levels also increased significantly, on an average by about 102% in roots and 74% in shoots of cv. satabdi compared to a rise, by about 49% in roots and 56% in shoots of cv. khitish. The elevated level of glutathione coincided with the stimulatory influence of Se on its regulatory enzymes. Concomitantly the levels of ?-tocopherol and phytochelatins were also induced in both the test cultivars. Increase in ?-tocopherol activity reached a maximum by about 47% in roots and 80% in shoots of cv. satabdi whereas it increased by about 36% in roots and about 64% in shoots of cv. khitish. Substantive increase in the levels of PC4 followed by PC2 and PC3 was also noted. The effects were found to be less conspicuous in shoots than in roots. Rice seedlings exposed to combined Se and 10mM sulphate treatments showed improved growth and development as a result of better thiol metabolism due to amelioration of the adverse effects caused by selenium alone on all the parameters tested

Ribonucleic acid polymerase from eukaryotic cells: effects of factors and rifampicin on the activity of RNA polymerase from chromatin of coconut nuclei

The role of protein factor B and C on RNA synthesis by RNA polymerase CI isolated from chromosomal non-histone proteins of coconut nuclei has been studied further. Factor B has been implicated as the initiation factor on the experimental evidences that (a) in its absence, RNA polymerase CI shows only minimal activity; (b) it can bind with RNA polymerase and the enzyme . factor B complex then binds to DNA, but factor B alone can not bind to DNA; (c) it promotes the incorporation of [β,-32P2]ATP into RNA and this stimulation reaches a plateau rather quickly while the incorporation of [14C]ATP in the interior of RNA chain continues; (d) it is active with native homologous DNA as template, but not with denatured or λ DNA; (e) RNA molecules synthesized in its presence are of higher sedimentation value (10-20 S) than that synthesized in its absence (4 S); (f) it can completely counteract the inhibitory effect of rifampicin, which is known to inhibit RNA synthesis at the initiation step. Factor C seems to facilitate the release of synthesized RNA from the DNA template since (a) it stimulates RNA synthesis by polymerase CI when added on top of factor B, but in absence of factor B, C alone is inactive; (b) it can reinitiate RNA synthesis after the reaction has reached a plateau in a system where DNA is limiting, an affect similar to that obtained at higher ionic strength. Factor C, however, does not influence the molecular size of RNA synthesized. Furthermore, the RNA polymerase CI is sensitive to α-amanitin whereas the RNA polymerase CII is comparatively resistant. The former appears to synthesize the non-ribosomal RNA whereas the latter synthesizes ribosomal RNA

Efficacy of seed priming strategies for enhancing salinity tolerance in plants: An overview of the progress and achievements

Soil salinization adversely affects sustainability and productivity of cultivable land by altering seed germination, growth and physio-biochemical attributes consequently limiting agricultural output. To sustain crop productivity, therefore, the need to comprehend plant tolerance mechanism becomes imperative. Enhancement of stress resilience can be achieved through several methods but here, we delineate a novel cost-effective ecofriendly technique known as priming, which involves pre-germinative exposure of seeds to eliciting factors that induce mild stress and fortifies plants against subsequent stressful constraints. Priming and sensitizing the seeds in different chemicals prior to sowing enhances its imbibition capacity and pre-germinative metabolic processes to improve seedling emergence, growth, vigour and productivity. Enhanced activity of Na+/H+antiporters in invigorated seedlings favour Na+ exclusion and K+ uptake thereby stabilizing membrane potential. Priming mediated memory upregulates expression of genes associated with giberrellic acid (GA) biosynthesis and photosynthesis that accelerates seedling emergence. Priming induced reprogramming of antioxidant genes and polyamine metabolism genes improve adaptability under salt stress. Seed priming also enhances DNA repair, stabilizes RNA, increases de novo protein synthesis to maintain genome integrity. This review presents a comprehensive update on the efficacy of seed priming, its associated physio-biochemical and molecular modulations that would aid to eradicate salt-induced adversities conferring tolerance to the primed plants and enhance productivity

NaCl pretreatment alleviates salt stress by enhancement of antioxidant defense system and osmolyte accumulation in mungbean (<i style="">Vigna radiata</i> L. Wilczek)

593-600Enhancement of salt (NaCl) tolerance by pretreatment with sublethal dose (50 mM) of NaCl was investigated in V. radiata seedlings. NaCl stress caused drastic effects on roots compared to shoots. Accompanying reductions in length, number of root hairs and branches, roots became stout, brittle and brown in color. Salt stress caused gradual reduction in chlorophyll, carotenoid pigment contents and chlorophyll fluorescence intensity also. Superoxide dismutase and catechol peroxidase activities increased under stress in both roots and leaves. But catalase activity showed an increase in roots and decrease in leaves. In these seedlings, the oxidative stress has been observed under salinity stress and the level of proline, H2O2 and malondialdehyde content were increased. But pretreatment with sublethal dose of NaCl was able to overcome the adverse effects of stress imposed by NaCl to variable extents by increasing growth and photosynthetic pigments of the seedlings, modifying the activities of antioxidant enzymes, reducing malondialdehyde and H2O2 content and increasing accumulation of osmolytes like proline. Thus, mungbean plants can acclimate to lethal level of salinity by pretreatment with sublethal level of NaCl, improving their health and production under saline condition

Immotilin, a novel sperm immobilizing protein

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