Project description:The salt glands in the epidermis of recretohalophytes play a pivotal role in salt tolerance by secreting excess salts from tissues. Irrespective of the importance of understanding the secretion process, nothing is known about the molecular mechanisms of salt gland development. Limonium bicolor possesses multi-cellular salt glands in the epidermis and provides a model to study salt gland development. We applied next-generation sequencing to profile early leaf development using five distinctly different developmental stages, which were quantified by successive collections of the first true leaf of L. bicolor with precise spatial and temporal resolution. Twenty-two percent of the genes were differentially expressed along the developmental gradient. Cluster analysis revealed specific expression patterns at one stage, and identified enriched functions specific for each developmental stage. Seventy-two genes were identified as highly involved in salt gland differentiation. Salt glands have high homology with trichomes, which was also confirmed by mutants with increased salt gland densities. A model is proposed to illustrate genes participating in salt gland differentiation. This unique dataset lays the foundation for identifying key genes involved in salt gland development and salt secretion, which is a requisite for understanding mechanisms that could make agriculture possible in saline areas worldwide.
Project description:Limonium bicolor, a typical recretohalophyte living in saline land, excretes excessive salt to the environment through salt glands in the epidermis for avoiding salt stress. The aim of this study was to screen genes involved in salt secretion by high-throughput RNA sequencing. A model was established to illustrate the candidate genes regulating salt secretion of salt gland. These genes will shed light on molecular mechanism of salt secretion of salt gland in plant.Normalized cDNA libraries of L. bicolor were constructed using mature leaves treated with 200 mM NaCl (with the highest salt secretion) and the control. Illumina paired-end platform was utilized to yield 2×100 bp independent reads. After de novo assembly, unigenes were aligned to the non-redundant (Nr) protein database and differentially expressed genes were enriched by GO annotations. Candidate genes were further verified by L. bicolor mutants with abnormal salt secretion.19,498 genes were targeted in Nr database and 5,768 were differentially expressed mapping to Arabidopsis, 2,269 up-regulated and 3,519 down-regulated under NaCl treatment compared with the control. Genes related to ion transport, vesicle, reactive oxygengen species scavenging, abscisic acid-dependent signal pathway and transcription factors were found high expression under NaCl treatment, of which 55 genes were likely involved in salt secretion and also confirmed by salt-secretion mutants.The present report identified candidate genes which are highly associated with salt secretion of L. bicolor salt gland. A salt transporting pathway was illustrated to explain how Na+ excreted outside by salt gland in L. bicolor. This data provides a useful reference source for salt secretion study of recretohalophytes.