RESUMEN
Submergence of plant organs perturbs homeostasis by limiting diffusion of oxygen, carbon dioxide and ethylene. In rice (Oryza sativa L.), the haplotype at the multigenic SUBMERGENCE1 (SUB1) locus determines whether plants survive prolonged submergence. SUB1 encodes two or three transcription factors of the group VII ethylene response factor family: SUB1A, SUB1B and SUB1C. The presence of SUB1A-1 and its strong submergence-triggered ethylene-mediated induction confers submergence tolerance through a quiescence survival strategy that inhibits gibberellin (GA)-induced carbohydrate consumption and elongation growth. SUB1C is invariably present and acts downstream of the enhancement of GA responsiveness during submergence. In this study, heterologous ectopic expression of rice SUB1A and SUB1C in Arabidopsis thaliana was used to explore conserved mechanisms of action associated with these genes using developmental, physiological and molecular metrics. As in rice transgenic plants that ectopically express SUB1A-1, Arabidopsis transgenic plants that constitutively express SUB1A displayed GA insensitivity and abscisic acid hypersensitivity. Ectopic SUB1C expression had more limited effects on development, stress responses and the transcriptome. Observation of a delayed flowering phenotype in lines over-expressing SUB1A led to the finding that inhibition of floral initiation is a component of the quiescence survival strategy in rice. Together, these analyses demonstrate conserved as well as specific roles for group VII ethylene response factors in integration of abiotic responses with development.
Asunto(s)
Adaptación Fisiológica , Arabidopsis/genética , Flores/fisiología , Oryza/genética , Proteínas de Plantas/metabolismo , Factores de Transcripción/metabolismo , Ácido Abscísico/farmacología , Arabidopsis/efectos de los fármacos , Arabidopsis/fisiología , Oscuridad , Flores/metabolismo , Perfilación de la Expresión Génica , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Germinación , Giberelinas/farmacología , Oryza/metabolismo , Fenotipo , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/fisiología , Proteínas de Plantas/genética , Plantas Modificadas Genéticamente/efectos de los fármacos , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/fisiología , Semillas/efectos de los fármacos , Semillas/fisiología , Factores de Transcripción/genéticaRESUMEN
Plants can reorient their organs in response to changes in environmental conditions. In some species, ethylene can induce resource-directed growth by stimulating a more vertical orientation of the petioles (hyponasty) and enhanced elongation. In this study on Arabidopsis (Arabidopsis thaliana), we show significant natural variation in ethylene-induced petiole elongation and hyponastic growth. This hyponastic growth was rapidly induced and also reversible because the petioles returned to normal after ethylene withdrawal. To unravel the mechanisms behind the natural variation, two contrasting accessions in ethylene-induced hyponasty were studied in detail. Columbia-0 showed a strong hyponastic response to ethylene, whereas this response was almost absent in Landsberg erecta (Ler). To test whether Ler is capable of showing hyponastic growth at all, several signals were applied. From all the signals applied, only spectrally neutral shade (20 micromol m(-2) s(-1)) could induce a strong hyponastic response in Ler. Therefore, Ler has the capacity for hyponastic growth. Furthermore, the lack of ethylene-induced hyponastic growth in Ler is not the result of already-saturating ethylene production rates or insensitivity to ethylene, as an ethylene-responsive gene was up-regulated upon ethylene treatment in the petioles. Therefore, we conclude that Ler is missing an essential component between the primary ethylene signal transduction chain and a downstream part of the hyponastic growth signal transduction pathway.