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The effects of silicon on water relations, photosynthetic gas exchange, and carboxylation activities of wheat (Triticum aestivum L.) leaves were investigated in field drought conditions. Silicon application improved the leaf relative water content and water potential under drought. The leaf net photosynthetic rate and stomatal conductance were significantly decreased between 7:30 and 17:30 under drought, whereas silicon application increased the leaf net photosynthetic rate between 7:30 and 15:30 with an exception at 9:30. Silicon application also increased the leaf stomatal conductance at 13:30 and 17:30 under drought. The leaf transpiration rate was decreased by drought but it was increased by silicon from 13:30 to 17:30. The intercellular CO₂ concentration was increased at 7:30 under drought, while it was decreased most of the time from midday to the afternoon. The leaf stomatal limitation was increased under drought from 11:30 to 17:30, whereas it was intermediate in silicon treated plants. The instantaneous water use efficiency was significantly increased by silicon application at 7:30 under drought. Silicon application slightly decreased the activity of ribulose-1, 5-bisphosphate carboxylase, but it increased the activity of phosphoenolpyruvate carboxylase and the concentration of inorganic phosphorus under drought. These results suggest that silicon could improve the photosynthetic ability of wheat in field drought conditions, and both stomatal and non-stomatal factors were involved in the regulation. In the early morning (at 7:30), the non-stomatal factor was the main contributor; 9:30 was a turning point, after which the stomatal factor was the main contributor.
For investigating the protective roles of antioxidative system in desiccation tolerance of Caragana species as they adapt to arid environments, we monitored a variety of ecophysiological parameters in the leaves of Caragana arborescens (mesophyte), C. microphylla (semiarid species), C. roborovskyi, C. stenophylla, C. acanthophylla, and C. tragacanthoides (xerophyte) grown under a drying-rehydration cycle. Relative leaf water content and chlorophyll content were decreased by 17.4–39.2 %, and by 14–40 %, respectively, after exposure to 48 days of drought stress. Malondialdehyde did not increase in xeric Caragana species. Hydrogen peroxide concentrations increased by 13.1–43.9 % except in C. acanthophylla. The activities of superoxide dismutase (SOD), guaiacol peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR) and reduced glutathione (GSH) in xeric Caragana species were significantly elevated with progressing drought stress. However, catalase in all species decreased markedly before drought stress treatment reached 40 days. The xeric Caragana species showed higher SOD, POD, APX, and GR activities, as well as ascorbate content, and more manganese SOD isoenzymes. C. arborescens and C. microphylla accumulated more free proline. Our data indicate that SOD and POD with the ascorbate–glutathione cycle have important protective effects in xeric Caragana species under drought stress. Free proline may be crucial in the resistance of C. arborescens and C. microphylla to drought stress.
Gibberellic acid (GA) is an important signaling molecule that participates in many aspects of plant growth and development. While the importance of this hormone is clear, the transcriptional regulatory networks involved are still being characterized. The cereal aleurone, particularly the barley aleurone, has been used as a classic model to study GA and GA signaling for many years, and these studies have significantly contributed to our understanding of GA in plant biology. The objective of this study was to characterize the transcripts regulated through the DELLA protein SLN1, a negative regulator of the GA signaling pathway. To detect the transcripts, Affymetrix Barley 1 GeneChips were hybridized with RNA extracted from barley aleurone treated with GA or aleurone of the DELLA mutant sln1c without GA treatment. The transcripts detected, in term of both expressed genes and their function, were highly similar between the GA-treatment and the sln1c mutant. These results from a genome-wide transcript analysis provide evidence that SLN1 in the GA signal transduction pathway controls almost all GA-induced genes in the barley aleurone.
In this study, we report the cloning and characteristics of an adiponectin-like receptor gene from Bombyx mori (BmAdipoR) with highly conserved deduced amino-acid sequences and similar structure to the human adiponectin receptor (AdipoR). Structural analysis of the translated cDNA suggested it encoded a membrane protein with seven transmembrane domains. BmAdipoR was found to be expressed in multiple tissues and highly expressed in Malpighian tubules, fat body and testis. BmNPV (Bombyx morinucleopolyhedrovirus) bacmid system combined with confocal microscopy revealed that BmAdipoR was targeted to the cell membrane. We also found that infection with BmNPV did not have an effect on BmAdipoR mRNA quantity in the midgut of susceptible Bombyx moristrain (306) at 48 h, but BmAdipoR mRNA quantity increased significantly at 72 h. We concluded that BmAdipoR gene was a membrane protein ubiquitously expressed in Bombyx moritissues and that its expression was altered by treating with BmNPV.
Serpins are a broadly distributed family of protease inhibitors. In this study, the gene encoding Bombyx mori serpin-2 (Bmserpin-2) was cloned and expressed in E. coli. The Bmserpin-2 cDNA contains a 1125 bp open reading frame (ORF). The deduced protein has 374 amino-acid residues, contains a conserved SERPIN domain and shares extensive homology with other invertebrate serpins. RT-PCR analysis showed that Bmserpin-2 was expressed in all developmental stages of B. mori larvae and various larval tissues. Subcellular localization analysis indicated that Bmserpin-2 protein was located in the cytoplasm. Interestingly, real-time quantitative PCR revealed that the expression of Bmserpin-2 in the midgut of susceptible B. mori strain 306 significantly increased at 72 hours post inoculation (hpi) when infected with BmNPV. However, there was no significant increase of the Bmserpin-2 expression in resistant strain NB infected with BmNPV. Thus, our data indicates that Bmserpin-2 may be involved in B. mori antiviral response.
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