High salinity is one of the main factors limiting cotton growth and productivity. The genes that regulate salt stress in TM-1 upland cotton were monitored using microarray and real-time PCR (RT-PCR) with samples taken from roots. Microarray analysis showed that 1503 probe sets were up-regulated and 1490 probe sets were down-regulated in plants exposed for 3h to 100mM NaCl, and RT-PCR analysis validated 42 relevant/related genes. The distribution of enriched gene ontology terms showed such important processes as the response to water stress and pathways of hormone metabolism and signal transduction were induced by the NaCl treatment. Some key regulatory gene families involved in abiotic and biotic sources of stress such as WRKY, ERF, and JAZ were differentially expressed. Our transcriptome analysis might provide some useful insights into salt-mediated signal transduction pathways in cotton and offer a number of candidate genes as potential markers of tolerance to salt stress.

Somatic embryo development (SED) in upland cotton shows low frequencies of embryo maturation and plantlet regeneration. Progress in increasing the regeneration rate has been limited. Here a global analysis of proteome dynamics between globular and cotyledonary embryos was performed using isobaric tags for relative and absolute quantitation to explore mechanisms underlying SED. Of 6318 proteins identified by a mass spectrometric analysis, 102 proteins were significantly up-regulated and 107 were significantly down-regulated in cotyledonary embryos. The differentially expressed proteins were classified into seven functional categories: stress responses, hormone synthesis and signal transduction, carbohydrate and energy metabolism, protein metabolism, cell wall metabolism, cell transport, and lipid metabolism. KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis showed that stress response, hormone homeostasis, and respiration and photosynthesis were involved in SED. Quantitative real-time PCR analysis confirmed the authenticity and accuracy of the proteomic analysis. Treatment of exogenous hormones showed that abscisic acid and jasmonic acid facilitate SED, whereas gibberellic acid inhibits SED and increases abnormal embryo frequency. Thus, global analysis of proteome dynamics reveals that stress response, hormone homeostasis, and respiration and photosynthesis determined cotton SED. The findings of this research improve the understanding of molecular processes, especially environmental stress response, involved in cotton SED.

The cotton diploid species, Gossypium arboreum, shows important properties of stress tolerance and good genetic stability. In this study, through mRNA-seq, we de novo assembled the unigenes of multiple samples with 3h H2O, NaCl, or PEG treatments in leaf, stem and root tissues and successfully obtained 123,579 transcripts of G. arboreum, 89,128 of which were with hits through BLAST against known cotton ESTs and draft genome of G. raimondii. About 36,961 transcripts (including 1,958 possible transcription factor members) were identified with differential expression under water stresses. Principal component analysis of differential expression levels in multiple samples suggested tissue selective signalling responding to water stresses. Venn diagram analysis showed the specificity and intersection of transcripts’ response to NaCl and PEG treatments in different tissues. Self-organized mapping and hierarchical cluster analysis of the data also revealed strong tissue selectivity of transcripts under salt and osmotic stresses. In addition, the enriched gene ontology (GO) terms for the selected tissue groups were differed, including some unique enriched GO terms such as photosynthesis and tetrapyrrole binding only in leaf tissues, while the stem-specific genes showed unique GO terms related to plant-type cell wall biogenesis, and root-specific genes showed unique GO terms such as monooxygenase activity. Furthermore, there were multiple hormone cross-talks in response to osmotic and salt stress. In summary, our multidimensional mRNA sequencing revealed tissue selective signalling and hormone crosstalk in response to salt and osmotic stresses in G. arboreum. To our knowledge, this is the first such report of spatial resolution of transcriptome analysis in G. arboreum. Our study will potentially advance understanding of possible transcriptional networks associated with water stress in cotton and other crop species.