Effect of fasting, branched-chain amino acids, and glucocorticoids on histone H1 extractability from rat skeletal muscle.

The effect of 72 h fasting, nutritional therapy of fasted rats, and acute and chronic glucocorticoid treatment on the yield of histone H1 from rat hind limb muscles was determined. Fasting significantly enhanced the extractability of muscle H1. The effect of treating starved rats with glucose alone, or with glucose supplemented with branched-chain amino acids (BCAA), or with two commercial preparations of mixtures of essential and non-essential amino acids was evaluated. Treatment of starved rats with glucose alone significantly decreased H1 extractability from muscles, but isocaloric treatment with glucose supplemented with BCAA or two commercial preparations of amino acid mixtures was more effective. Glucocorticoid treatment for 5 days enhanced the yield of H1 from muscles less than starvation. The enhanced H1 extractability from muscles noted in starved rats is similar to that reported in rats with insulinopenic diabetes and may reflect changes in nuclear fragility.     

Temporal Regulation of Somatic Embryogenesis by Adjusting Cellular Polyamine Content in Eggplant

Four critical stages of embryogenesis, including callus induction, cellular acquisition of morphogenetic competence, expression of embryogenic program, and development and maturation of somatic embryos during somatic embryogenesis from leaf discs of eggplant (Solanum melongena L.), were identified by scanning electron microscopy. Temporal changes in arginine decarboxylase (ADC) activity and polyamines (PAs) during critical stages of embryogenesis revealed that high levels of PAs (especially putrescine [PUT]), due to higher ADC activity in discs from the apical region (with high embryogenic capacity) than from the basal region of the leaf (with poor embryogenic capacity), were correlated with differential embryogenesis response. Kinetic studies of the up- and down-regulation of embryogenesis revealed that PUT and difluoromethylarginine pretreatments were most effective before the onset of embryogenesis. Basal discs pretreated with PUT for 4 to 7 d showed improved embryogenesis that was comparable to apical discs. PA content at various critical steps in embryogenesis from basal discs were found to be comparable to that of apical discs following adjustments of cellular PA content by PUT. In contrast, pretreatment of apical discs with difluoromethylarginine for 3 d significantly reduced ADC activity, cellular PA content, and embryogenesis to levels that were comparable to basal discs. Discs from the basal region of leaves treated with PUT for 3 d during the identified stages of embryogenesis improved their embryogenic potential.     

Emerging Molecular Strategies for Improving Rice Drought Tolerance

Rice occupies a pre-eminent position as a food crop in the world. Its production, how- ever, entails up to 3000 liters of water per kilogram of grain produced. Such high demand makes rice prone to drought easily. Sustainable rice cultivation with limited water resources requires the deployment of a suitable strategy for better water use efficiency and improved drought tolerance. Several drought-related genes have been evaluated in rice for their mode of action in conferring drought tolerance. Manipulation of components of abscisic acid signal transduction, stomatal density, deposition of cuticular wax, and protein modification pathways are emerging as priority targets. Gene reprogramming by microRNAs is also being explored to achieve drought tolerance. Genetically dissected Quantitative Trait Loci (QTLs) and their constituent genes are being deployed to develop drought-tolerant rice varieties. Progressive research and challenges include a better understanding of crucial components of drought response and search for new targets and the deployment of improved varieties in the field.