Cloning and expression analysis of GhDET3, a vacuolar H+ -ATPase subunit C gene, from cotton

Combined elevated temperature and soil waterlogging stresses limit fibre biomass accumulation and fibre quality formation by disrupting protein activity during cotton fibre development

Soil waterlogging and high temperature conditions generally occur together, especially in the Yangtze River Valley, China, negatively affecting cotton (Gossypium hirsutum L.) fibre development. Therefore, combined elevated temperature (34.1/29.0°C) and soil waterlogging (6 days) were imposed to study their combined effects on fibre biomass and fibre qualities (length, strength and micronaire). The results showed that in the boll cohort exposed to waterlogging and/or elevated air temperature, combined elevated temperature and soil waterlogging decreased final fibre length (by 8.9-11.3%) and fibre biomass (by 25.8-33.9%) more than either stress individually. A total of 113, 263 and 290 differential abundance proteins were identified related to elevated temperature, waterlogging and the two treatments combined, respectively, in fibres at 15 days after anthesis via the isobaric tags for relative and absolute quantitation technique, which were classified as: carbohydrate and energy metabolism (21.7%), protein metabolism (16.6%), amino acid metabolism (12.8%), intracellular structural components (6.6%), transport (7.9%), oxidation-reduction process (7.9%), signal transduction (5.2%), lipid metabolism (5.2%), stress response (5.2%), nucleic acid metabolism (4.5%), organic acid metabolism (3.4%) and others (2.1%). Both vacuolar ATPase (V-ATPase) and plasma membrane H+-ATPase (PMH+-ATPase) were responsible for fibre length formation, although V-ATPase expression may play a major role in determining fibre cell elongation rather than PM H+-ATPase expression. It was concluded that fibre cell elongation and secondary wall thickening were inhibited mainly by reduced accumulation of osmolytes, blocked synthesis and transport of secondary wall components, and disruption of the cytoskeleton system under combined elevated temperature and soil waterlogging.

Cryptochrome 1 regulates growth and development in Brassica through alteration in the expression of genes involved in light, phytohormone and stress signalling

The blue light photoreceptors cryptochromes are ubiquitous in higher plants and are vital for regulating plant growth and development. In spite of being involved in controlling agronomically important traits like plant height and flowering time, cryptochromes have not been extensively characterized from agriculturally important crops. Here we show that overexpression of CRY1 from Brassica napus (BnCRY1), an oilseed crop, results in short-statured Brassica transgenics, likely to be less prone to wind and water lodging. The overexpression of BnCRY1 accentuates the inhibition of cell elongation in hypocotyls of transgenic seedlings. The analysis of hypocotyl growth inhibition and anthocyanin accumulation responses in BnCRY1 overexpressors substantiates that regulation of seedling photomorphogenesis by cry1 is dependent on light intensity. This study highlights that the photoactivated cry1 acts through coordinated induction and suppression of specific downstream genes involved in phytohormone synthesis or signalling, and those involved in cell wall modification, during de-etiolation of Brassica seedlings. The microarray-based transcriptome profiling also suggests that the overexpression of BnCRY1 alters abiotic/biotic stress signalling pathways; the transgenic seedlings were apparently oversensitive to abscisic acid (ABA) and mannitol.

A gene expression analysis of syncytia laser microdissected from the roots of the Glycine max (soybean) genotype PI 548402 (Peking) undergoing a resistant reaction after infection by Heterodera glycines (soybean cyst nematode)

The syncytium is a nurse cell formed within the roots of Glycine max by the plant parasitic nematode Heterodera glycines. Its development and maintenance are essential for nematode survival. The syncytium appears to undergo two developmental phases during its maturation into a functional nurse cell. The first phase is a parasitism phase where the nematode establishes the molecular circuitry that during the second phase ensures a compatible interaction with the plant cell. The cytological features of syncytia undergoing susceptible or resistant reactions appear the same during the parasitism phase. Depending on the outcome of any defense response, the second phase is a period of syncytium maintenance (susceptible reaction) or failure (resistant reaction). In the analyses presented here, the localized gene expression occurring at the syncytium during the resistant reaction was studied. This was accomplished by isolating syncytial cells from Glycine max genotype Peking (PI 548402) by laser capture microdissection. Microarray analyses using the Affymetrix soybean GeneChip directly compared Peking syncytia undergoing a resistant reaction to those undergoing a susceptible reaction during the parasitism phase of the resistant reaction. Those analyses revealed lipoxygenase-9 and lipoxygenase-4 as the most highly induced genes in the resistant reaction. The analysis also identified induced levels of components of the phenylpropanoid pathway. These genes included phenylalanine ammonia lyase, chalcone isomerase, isoflavone reductase, cinnamoyl-CoA reductase and caffeic acid O-methyltransferase. The presence of induced levels of these genes implies the importance of jasmonic acid and phenylpropanoid signaling pathways locally at the site of the syncytium during the resistance phase of the resistant reaction. The analysis also identified highly induced levels of four S-adenosylmethionine synthetase genes, the EARLY-RESPONSIVE TO DEHYDRATION 2 gene and the 14-3-3 gene known as GENERAL REGULATORY FACTOR 2. Subsequent analyses studied microdissected syncytial cells at 3, 6 and 9 days post infection (dpi) during the course of the resistant reaction, resulting in the identification of signature gene expression profiles at each time point in a single G. max genotype, Peking.

Enrichment of a set of microRNAs during the cotton fiber development

Background

Cotton (Gossypium hirsutum) is one of the most important economic crops and provides excellent fibers for textile manufacture. In addition to its industrial and agricultural importance, the fiber cell (plant trichome) also is a biological model system for exploring gene expression and regulation. Small RNAs regulate many aspects of plant growth and development. However, whether small RNAs are involved in regulation of fiber cell development is unknown.

Results

We adopted a deep sequencing approach developed by Solexa (Illumina Inc.) to investigate global expression and complexity of small RNAs during cotton fiber initiation and development. We constructed two small RNA libraries prepared from wild type (WT) and fuzz/lintless (fl Mutant in the WT background) cotton ovules, respectively. Each library was sequenced individually and generated more than 6-7 million short sequences, resulting in a total of over 13 million sequence reads. At least 22 conserved candidate miRNA families including 111 members were identified. Seven families make up the vast majority of expressed miRNAs in developing cotton ovules. In total 120 unique target genes were predicted for most of conserved miRNAs. In addition, we identified 2 cell-type-specific novel miRNA candidates in cotton ovules. Our study has demonstrated significant differences in expression abundance of miRNAs between the wild-type and mutant, and suggests that these differentially expressed miRNAs potentially regulate transcripts distinctly involved in cotton fiber development.

Conclusion

The present study is the first to deep sequence the small RNA population of G. hirsutum ovules where cotton fibers initiate and develop. Millions of unique miRNA sequences ranging from 18~28 nt in length were detected. Our results support the importance of miRNAs in regulating the development of different cell types and indicate that identification of a comprehensive set of miRNAs in cotton fiber cells would facilitate our understanding of the regulatory mechanisms for fiber cell initiation and elongation.