Transcriptome of NaCl-treated Limonium bicolor Leaves to Reveal How Many Genes Control Salt Secretion

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. Overall design: The control and NaCl-treated leaves were used as samples to analyze the transcriptome changes under salt treatment.