The transcriptome of NaCl-treated Limonium bicolor leaves reveals the genes controlling salt secretion of salt gland

Abstract

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.

Making Plants Break a Sweat: the Structure, Function, and Evolution of Plant Salt Glands

“…Transcriptomic analysis of developing Limonium bicolor leaves while monitoring salt gland developmental stages suggests that salt gland development might be regulated by transcription factors homologous to those regulating trichome development in Arabidopsis thaliana , however, this suggestion is based solely on correlated expression patterns and weakly documented evidence for orthology (Yuan et al, 2015b, 2016b). Yuan et al (2014) have further developed a transformation system for L. bicolor to enable validation of predicted gene functions within the native genome.…”

“…Faraday and Thomson (1986a) reported ion efflux rates in Limonium perezii salt glands that were significantly higher than rates possible exclusively via transmembrane transport. Congruently, Yuan et al (2016b) have reported genes associated with vesicle function enriched in Limonium bicolor leaves upon NaCl treatment. Vesicle-mediated NaCl transport may provide the energy efficiency required for transporting salts through the salt glands that may not be feasible via transmembrane ion channels alone.…”

“…Vesicle-mediated NaCl transport may provide the energy efficiency required for transporting salts through the salt glands that may not be feasible via transmembrane ion channels alone. Physiological and molecular studies have attempted to model the unidirectional flux of Na + and Cl - in multicellular salt glands of Limonium and Avicennia (Tan et al, 2013; Yuan et al, 2016b), but the details of the cell-specific roles in any multicellular salt gland remain largely unknown.…”

Therapeutic targeting of cellular stress responses in cancer

“…Reactive oxygen species (ROS), such as superoxide anion radicals, hydroxyl radicals, and hydrogen peroxide, are natural by‐products of aerobic metabolism . In cells, mitochondria are the primary source of endogenous intracellular reactive species.…”

Molecular mechanisms underlying stress response and adaptation

“…These stresses can affect nutrient uptake and utilization; therefore, plants have developed a wide variety of structural, morphological, and regulatory adaptations to address these environmental stresses . In particular, multi‐level regulatory mechanisms involved in salt tolerance have been well characterized in halophytes, such as Suaeda salsa, Thellungiella salsuginea , and Limonium bicolor . Adaptations to cold stress, drought, and UV radiation have also been reported to a lesser degree.…”