RESUMEN
Small RNAs (sRNAs) are short, non-coding, 17-24 nucleotides long RNA molecules that play vital roles in regulating gene expression in every known organism investigated to date including cotton (Gossypium ssp.). These tiny RNA molecules target diverse categories of genes from different bioliogical and metabolic processes and have been reported in the three domains of life. Small RNAs, including miRNAs, are involved in ovule and fiber development, biotic and abiotic stresses, fertility, and other biochemical processes in cotton species. Also, sRNAs are the critical components in RNA interference pathway. In this article, we have reviewed the research efforts related to the isolation and characterization of miRNAs using molecular and genomic approaches. The progress made in understanding the functional roles of miRNAs in regulation, alteration, and inactivation of fundamental plant processes and traits of importance in cotton are presented here.
Asunto(s)
Productos Agrícolas/genética , Gossypium/genética , MicroARNs/genética , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Gossypium/crecimiento & desarrollo , MicroARNs/metabolismo , Fitomejoramiento/métodos , Carácter Cuantitativo HeredableRESUMEN
Transcription profiling analysis identified Saccharum hybrid DIRIGENT (SHDIR16) and Omicron-Methyltransferase (SHOMT), putative defense and fiber biosynthesis-related genes that are highly expressed in the stem of sugarcane, a major sucrose accumulator and biomass producer. Promoters (Pro) of these genes were isolated and fused to the beta-glucuronidase (GUS) reporter gene. Transient and stable transgene expression analyses showed that both Pro( DIR16 ):GUS and Pro( OMT ):GUS retain the expression characteristics of their respective endogenous genes in sugarcane and function in orthologous monocot species, including rice, maize and sorghum. Furthermore, both promoters conferred stem-regulated expression, which was further enhanced in the stem and induced in the leaf and root by salicylic acid, jasmonic acid and methyl jasmonate, key regulators of biotic and abiotic stresses. Pro( DIR16 ) and Pro( OMT ) will enable functional gene analysis in monocots, and will facilitate engineering monocots for improved carbon metabolism, enhanced stress tolerance and bioenergy production.
Asunto(s)
Regulación de la Expresión Génica de las Plantas , Metiltransferasas/genética , Proteínas de Plantas/genética , Tallos de la Planta/genética , Regiones Promotoras Genéticas , Saccharum/enzimología , Saccharum/genética , Acetatos/farmacología , Secuencia de Aminoácidos , Secuencia de Bases , Ciclopentanos/farmacología , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Genes de Plantas/genética , Glucuronidasa/metabolismo , Lignina/metabolismo , Datos de Secuencia Molecular , Especificidad de Órganos/efectos de los fármacos , Especificidad de Órganos/genética , Oryza/anatomía & histología , Oryza/citología , Oryza/efectos de los fármacos , Oryza/genética , Oxilipinas/farmacología , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Tallos de la Planta/citología , Tallos de la Planta/efectos de los fármacos , Plantas Modificadas Genéticamente , Saccharum/efectos de los fármacos , Ácido Salicílico/farmacología , Alineación de Secuencia , Sorghum/efectos de los fármacos , Sorghum/genética , Estrés Fisiológico/efectos de los fármacos , Estrés Fisiológico/genética , Zea mays/efectos de los fármacos , Zea mays/genéticaRESUMEN
Mycoparasitic fungi are proving to be rich sources of antifungal genes that can be utilized to genetically engineer important crops for resistance against fungal pathogens. We have transformed cotton and tobacco plants with a cDNA clone encoding a 42 kDa endochitinase from the mycoparasitic fungus, Trichoderma virens. Plants from 82 independently transformed callus lines of cotton were regenerated and analysed for transgene expression. Several primary transformants were identified with endochitinase activities that were significantly higher than the control values. Transgene integration and expression was confirmed by Southern and Northern blot analyses, respectively. The transgenic endochitinase activities were examined in the leaves of transgenic tobacco as well as in the leaves, roots, hypocotyls and seeds of transgenic cotton. Transgenic plants with elevated endochitinase activities also showed the expected 42 kDa endochitinase band in fluorescence, gel-based assays performed with the leaf extracts in both species. Homozygous T2 plants of the high endochitinase-expressing cotton lines were tested for disease resistance against a soil-borne pathogen, Rhizoctonia solani and a foliar pathogen, Alternaria alternata. Transgenic cotton plants showed significant resistance to both pathogens.
RESUMEN
The CaMV 35S promoter is the most commonly used promoter for driving transgene expression in plants. Though it is presumed to be a constitutive promoter, some reports suggest that it is not expressed in all cell types. In addition, the information available on its expression profile in all possible cell and tissue types and during early stages of development is incomplete. We present here a detailed expression profile of this promoter investigated using the green fluorescent protein (GFP) gene as a reporter system in cotton during embryo development, and in all the vegetative and floral cell and tissue types. GFP expression was not detected during the early stages of embryogenesis. The first perceptible GFP expression was observed in a small area at the junction of hypocotyl and cotyledons in embryos at around 13 days after anthesis. The GFP fluorescence progressively became stronger and expanded throughout the cotyledon and hypocotyl as embryo development advanced. After germination, varying levels of promoter activity were observed in all cell and tissue types in the hypocotyl, cotyledon, stem, leaf, petiole, and root. The promoter was also expressed in all floral parts. Although cotton pollen exhibited a low level of greenish autofluorescence, it was possible to discern GFP-dependent fluorescence in some of the pollen from all the T0 plants examined. Developing cotton fibers also exhibited GFP fluorescence suggesting that the 35S promoter was active in these specialized epidermal cells. Thus, we show that the expression of the 35S promoter was developmentally regulated during embryogenesis and that beyond a certain stage during embryogenesis, the promoter was expressed in most cell and tissue types in cotton albeit at different levels.