RESUMEN
Limonium bicolor, a typical recretohalophyte that lives in saline environments, excretes excessive salt to the environment through epidermal salt glands to avoid salt stress. The aim of this study was to screen for L. bicolor genes involved in salt secretion by high-throughput RNA sequencing. We established the experimental procedure of salt secretion using detached mature leaves, in which the optimal salt concentration was determined as 200 mM NaCl. The detached salt secretion system combined with Illumina deep sequencing were applied. In total, 27,311 genes were annotated using an L. bicolor database, and 2040 of these genes were differentially expressed, of which 744 were up-regulated and 1260 were down-regulated with the NaCl versus the control treatment. A gene ontology enrichment analysis indicated that genes related to ion transport, vesicles, reactive oxygen species scavenging, the abscisic acid-dependent signaling pathway and transcription factors were found to be highly expressed under NaCl treatment. We found that 102 of these genes were likely to be involved in salt secretion, which was confirmed using salt-secretion mutants. The present study identifies the candidate genes in the L. bicolor salt gland that are highly associated with salt secretion. In addition, a salt-transporting pathway is presented to explain how Na(+) is excreted by the salt gland in L. bicolor. These findings will shed light on the molecular mechanism of salt secretion from the salt glands of plants.
Asunto(s)
Hojas de la Planta/genética , Plumbaginaceae/genética , Plantas Tolerantes a la Sal/genética , Transcriptoma/genética , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Regulación de la Expresión Génica de las Plantas/fisiología , Genes de Plantas/genética , Genes de Plantas/fisiología , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/fisiología , Plumbaginaceae/efectos de los fármacos , Plumbaginaceae/fisiología , Tolerancia a la Sal/efectos de los fármacos , Tolerancia a la Sal/genética , Tolerancia a la Sal/fisiología , Plantas Tolerantes a la Sal/efectos de los fármacos , Plantas Tolerantes a la Sal/fisiología , Cloruro de Sodio/farmacología , Transcriptoma/fisiologíaRESUMEN
With the expansion of saline land worldwide, it is essential to establish a model halophyte to study the salt-tolerance mechanism. The salt glands in the epidermis of Limonium bicolor (a recretohalophyte) play a pivotal role in salt tolerance by secreting excess salts from tissues. Despite the importance of salt secretion, nothing is known about the molecular mechanisms of salt gland development. In this study, we applied RNA sequencing to profile early leaf development using five distinct developmental stages, which were quantified by successive collections of the first true leaves of L. bicolor with precise spatial and temporal resolution. Specific gene expression patterns were identified for each developmental stage. In particular, we found that genes controlling salt gland differentiation in L. bicolor may evolve in a trichome formation, which was also confirmed by mutants with increased salt gland densities. Genes involved in the special ultrastructure of salt glands were also elucidated. Twenty-six genes were proposed to participate in salt gland differentiation. Our dataset sheds light on the molecular processes underpinning salt gland development and thus represents a first step towards the bioengineering of active salt-secretion capacity in crops.
