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Abstract: Reference genes are critical for normalization of the gene expression level of target genes. The widely used housekeeping genes may change their expression levels at different tissue under different treatment or stress conditions. Therefore, systematical evaluation on the housekeeping genes is required for gene expression analysis. Up to date, no work was performed to evaluate the housekeeping genes in cotton under stress treatment. In this study, we chose 10 housekeeping genes to systematically assess their expression levels at two different tissues (leaves and roots) under two different abiotic stresses (salt and drought) with three different concentrations. Our results show that there is no best reference gene for all tissues at all stress conditions. The reliable reference gene should be selected based on a specific condition. For example, under salt stress, UBQ7, GAPDH and EF1A8 are better reference genes in leaves; TUA10, UBQ7, CYP1, GAPDH and EF1A8 were better in roots. Under drought stress, UBQ7, EF1A8, TUA10, and GAPDH showed less variety of expression level in leaves and roots. Thus, it is better to identify reliable reference genes first before performing any gene expression analysis. However, using a combination of housekeeping genes as reference gene may provide a new strategy for normalization of gene expression. In this study, we found that combination of four housekeeping genes worked well as reference genes under all the stress conditions. [Copyright &y& Elsevier]

Abstract: MicroRNAs (miRNAs) are an important gene regulator, controlling almost all biological and metabolic processes, in both plants and animals. In this study, we investigated the effect of drought and salinity stress on the expression of miRNAs and their targets in cotton (Gossypium hirsutum L.). Our results show that the expression change of miRNAs and their targets were dose-dependent and tissue-dependent under salinity and drought conditions. The expression of miRNAs in leaf was down-regulated under higher salinity stress while shows variable patterns in other conditions. The highest fold-changes of miRNAs were miR398 in roots with 28.9 fold down-regulation under 0.25% NaCl treatment and miR395 in leaves with 7.6 fold down-regulation under 1% PEG treatment. The highest up-regulation of miRNA targets was AST in roots with 4.7 fold-change under 2.5% PEG and the gene with highest down-regulation was CUC1 in leaves with 25.6 fold-change under 0.25% NaCl treatment. Among seven miRNA-target pairs we studied, five pairs, miR156–SPL2, miR162–DCL1, miR159–TCP3, miR395–APS1 and miR396–GRF1, show significant regulation relationship in roots and leaves under salinity stress concentration. [Copyright &y& Elsevier]

Grafting desirable scion on stress-tolerant rootstocks provides an opportunity to improve the cryotolerance of scion. Genic male sterile (GMS) lines of plant could be used as sterile line and maintainer in breeding, and they have the conspicuous characteristics that the fertility of which is easy to regain but hard to maintain by sexual reproduction. In order to maintain the fertility of GMS cotton by means of its perennial growth on the basis of frostless winters in Nanning, Guangxi autonomous region, GMS line A4 was grafted onto 7 cryotolerant rootstocks (F118, F697, F098, F112, F113, P098 and P113), and the cryotolerance and the overwintering survivorship of scions were investigated. In consequence, when compared with control (self-grafted A4), the relative conductivity of the grafted plants in shoot bark was reduced (8.80%), the content of soluble sugar, soluble protein and free proline were higher, 25.00, 1.55, 3.46%, respectively; the overwintering survival rate and the height of regeneration bud under field condition of grafted plants were higher, 10.44, 15.75%, respectively; the order of the grafted plants based on the average subordinate function value of overwintering survivorship was A4/F113>A4/F118>A4/F098>A4/F697>A4/F112>A4/P098>A4/P113>A4/A4(CK); the correlation analyses indicated that the physiological parameters of cryotolerance could be used for forecasting the overwintering survivorship, and the relative conductivity could be chosen as the first physiological parameter for forecasting cryotolerance or overwintering survivorship. The results indicate that the cryotolerance and the overwintering survivorship of GMS cotton could be improved by grafting, and F113 appeared to be a valuable rootstock. [ABSTRACT FROM AUTHOR]