SummaryHigh temperature stress disturbs cellular homoeostasis and results in a severe retardation in crop growth and development. Thus, it is important to reveal the mechanism of plants coping with heat stress. In this study, a novel gene that we identified from Brassica napus, referred to as BnTR1, was found to play a key role in heat stress response in planta. BnTR1 is a membranebound RINGv (C 4 HC 3 ) protein that displays E3 ligase activity in vitro. We demonstrated that modest expression of BnTR1 is sufficient to minimize adverse environmental influence and confers thermal resistance on development without any detrimental effects in B. napus and Oryza sativa. Our investigation into the action mechanism indicates that BnTR1 is likely to be involved in mediating Ca 2+ dynamics by regulating the activity of calcium channels, which further alters the transcripts of heat shock factors and heat shock proteins contributing to plant thermotolerance. Hence, our study identified BnTR1 as a novel key factor underlying a conserved mechanism conferring thermal resistance in plants.

Drought is believed to cause many metabolic changes which affect plant growth and development. However, it might be mitigated by various inorganic substances, such as nitrogen. Thus, the study was carried out to investigate the effect of foliar-applied urea with or without urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) on a maize cultivar under drought stress simulated by 15% (w/v) polyethylene glycol 6000. Foliar-applied urea resulted in a significant increase in plant dry weight, relative water content, and photosynthetic pigments under water stress condition. Furthermore, the activities of superoxide dismutase (SOD), peroxidase (POD), and hydrogen peroxidase (CAT), were enhanced with all spraying treatments under drought stress, which led to decreases in accumulation of hydrogen peroxide (HO), superoxide anion ([Formula: see text]) and malondialdehyde (MDA). The contents of soluble protein and soluble sugar accumulated remarkably with urea-applied under drought stress condition. Moreover, a further enhancement in above metabolites was observed by spraying a mixture of urea and urease inhibitor as compared to urea sprayed only. Taken together, our findings show that foliar application of urea and a urease inhibitor could significantly enhance drought tolerance of maize through protecting photosynthetic apparatus, activating antioxidant defense system and improving osmoregulation.

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Additional index words. adventitious bud formation, globular embryo, torpedo-type embryo, embryogenic callus, mass propagation Abstract. In persimmon, plant regeneration from cultured cells usually takes place through adventitious bud formation. If somatic embryogenesis were possible, the efficiency of mass propagation and genetic engineering would be greatly improved. We attempted to induce somatic embryogenesis from immature embryos and plant regeneration from the induced embryos. Hypocotyls and cotyledons from immature 'Fuyu' and 'Jiro' seeds were cultured in the dark in Murashige and Skoog medium solidified with gellan gum and supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzyladenine (BA) at various concentrations. Callus formation started at ' '2 weeks of culture, and the callus formation rate was highest at 3 or 10 mM combinations of 2,4-D and BA. The initially formed calli gradually became brown or black from which white embryogenic calli (EC) appeared secondarily. After ' '8 weeks of culture, globular embryos were formed from these EC, and the formation proceeded until 20 weeks of culture. Formation of globular embryos was higher with 'Fuyu' than 'Jiro', especially with hypocotyls. When EC with globular embryos were transferred to fresh medium with no plant growth regulators, ' '70% developed to the torpedo-type embryo stage in 6 weeks. The torpedo-type embryos thus formed were germinated and rooted in agar medium with or without zeatin in several weeks without entering dormancy. After germination and rooting, the plantlets were transferred to the same medium and acclimatized for another 4 weeks. As the embryos germinated and rooted simultaneously, the plantlets were easy to grow in pots without transplanting shock. This is the first report on plant regeneration through somatic embryogenesis of persimmon.