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Powdery mildew, which is caused by Blumeria graminis f. sp. tritici (Bgt), is a disease of wheat worldwide. Xiaobaidong is a Chinese wheat landrace, which still maintains good resistance against powdery mildew. To obtain more genetic markers closely linked to the powdery mildew resistance gene mlxbd and narrow the candidate region for its isolation, new simple sequence repeats and cross intron-spanning markers were designed based on the genome sequence of Triticum aestivum cultivar Chinese Spring chromosome 7BL. The flanking markers 7BLSSR49 and WGGC5746 were found to be tightly linked to mlxbd at genetic distances of 0.4 cM and 0.3 cM, respectively. The resistance locus was mapped to a 63.40 kb and 0.29 Mb region of the Chinese Spring genome and Zavitan genome, respectively. The linked markers of mlxbd could be used as diagnostic markers for mlxbd. The linked molecular markers and delineated genomic region in the sequenced Chinese Spring genome will assist the future map-based cloning of mlxbd.

Cottonseed oil has become an important source of edible oil due to its significant cost advantage. However, there is a growing concern over its fatty acid composition and nutritional value. In Gossypium hirsutum, GhFAD2-1 and GhFATB encoding the microsomal oleate desaturase and palmitoyl-acyl carrier protein thioesterase, respectively, play critical roles in regulating the proportions of saturated and polyunsaturated fatty acids in cottonseed lipids. In this study, RNAi technology was used to simultaneously inhibit the expression levels of GhFAD2-1 and GhFATB to improve the quality of cottonseed oil by increasing oleic acid content. Transgenic cotton plants with reduced levels of both target genes were successfully generated. In mature seed kernels of transgenic plants, the content of oleic acid was 38.25%, accordingly increasing by 156.96%, while the content of palmitic acid and linoleic acid was 19.15% and 36.68%, decreasing by 21.28% and 33.92%, respectively, compared with that of the control. The total oil content in transgenic and control kernels was 22.48% and 29.83%, respectively. The reduced oil level in transgenic seeds was accompanied by a reduction in seed index, thereby causing disadvantageous effects on seed germination potentiality and seed vigor, particularly under cool stress conditions. Our results demonstrated the feasibility of simultaneous manipulation of multiple genes using RNAi technology and showed the important role of oil content in seed development and vigor. Our findings provide insight into the physiological significance of the fatty acid composition in cottonseeds.

Many reports showed that polyamine oxidase (PAO) genes play crucial roles in various abiotic and biotic stresses response. In this study, 12 putative PAO genes (GhPAO 1 –GhPAO 12 ) were identified in upland cotton (Gossypium hirsutum L.) genome using the released genome database. A total of 349 cis-acting factors involved in hormone and stress response were predicted in 1.5-kb promoter regions at the upstream region of GhPAOs. These GhPAOs can be divided into four major groups when compared with their counterparts in Arabidopsis thaliana. Transcriptional level of GhPAOs were detected by qRT-PCR showing the highest levels in roots. Although GhPAOs exhibited various responses to NaCl treatment, the highest expression level was observed from 3 or 6 h after treatment. To further elucidate GhPAOs functions, GhPAO 3 were selected for genetic transformation in Arabidopsis. The content of spermine was significantly decreased in transgenic Arabidopsis lines, whereas the content of putrescine was enhanced, which indicates a potential role of GhPAO 3 in the conversion of spermidine and spermine. Discrepancy of salt resistance were observed in germination and seedling stage, which might be controlled by H2O2 concentration threshold. This study provides a valuable insight of the PAO genes in upland cotton response to abiotic stress.

Key message iTRAQ based proteomic identified key proteins and provided new insights into the molecular mechanisms underlying somatic embryogenesis in cotton. Abstract Somatic embryogenesis, which involves cell dedifferentiation and redifferentiation, has been used as a model system for understanding molecular events of plant embryo development in vitro. In this study, we performed comparative proteomics analysis using samples of non-embryogenic callus (NEC), embryogenic callus (EC) and somatic embryo (SE) using the isobaric tags for relative and absolute quantitation (iTRAQ) technology. In total, 5892 proteins were identified amongst the three samples. The majority of these proteins (93.4%) were found to have catalytic activity, binding activity, transporter activity or structural molecular activity. Of these proteins, 1024 and 858 were differentially expressed in NEC versus EC and EC versus SE, respectively. Compared to NEC, EC had 452 and 572 down- and up-regulated proteins, respectively, and compared to EC, SE had 647 and 221 down- and up-regulated proteins, respectively. KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis indicated that genetic information transmission, plant hormone transduction, glycolysis, fatty acid biosynthesis and metabolism, galactose metabolism were the top pathways involved in somatic embryogenesis. Our proteomics results not only confirmed our previous transcriptomic results on the role of the polyamine metabolic pathways and stress responses in cotton somatic embryogenesis, but identified key proteins important for cotton somatic embryogenesis and provided new insights into the molecular mechanisms underlying somatic embryogenesis in cotton.

Plant regeneration via somatic embryogenesis (SE) is the key step for genetic improvement of cotton (Gossypium hirsutum L.) through genetic engineering mediated by Agrobacteria, but the molecular mechanisms underlying SE in cotton is still unclear. Here, RNA-Sequencing was used to analyze the genes expressed during SE and their expression dynamics using RNAs isolated from non-embryogenic callus (NEC), embryogenic callus (EC) and somatic embryos (SEs). A total of 101, 670 unigenes were de novo assembled. The genes differentially expressed (DEGs) amongst NEC, EC and SEs were identified, annotated and classified. More DEGs were found between SEs and EC than between EC and NEC. A significant number of DEGs were related to hormone homeostasis, stress and ROS responses, and metabolism of polyamines. To confirm the expression dynamics of selected DEGs involved in various pathways, experiments were set up to investigate the effects of hormones (Indole-3-butytric acid, IBA; Kinetin, KT), polyamines, H2O2 and stresses on SE. Our results showed that exogenous application of IBA and KT positively regulated the development of EC and SEs, and that polyamines and H2O2 promoted the conversion of EC into SEs. Furthermore, we found that low and moderate stress is beneficial for proliferation of EC and SEs formation. Together, our global analysis of transcriptomic dynamics reveals that hormone homeostasis, polyamines, and stress response synergistically regulating SE in cotton. Electronic supplementary material The online version of this article (doi:10.1007/s11103-016-0511-6) contains supplementary material, which is available to authorized users.