Ion accumulation and expression of ion homeostasis-related genes associated with halophilism, NaCl-promoted growth in a halophyte Mesembryanthemum crystallinum L.

Abstract

A halophyte, the common ice plant (Mesembryanthemum crystallinum L.), shows the maximal growth under salinity, in which almost all crops die. The NaCl-stimulated growth, which is referred to as halophilism, is an important trait for adaptation to salinity, but the mechanism is still unclear. To elucidate factors contributing to the halophilism, we tested the effects of NaCl on growth, ion accumulation, and expression of ion homeostasis-related genes in suspension-cultured cells. Among nine ions analyzed, Na + , Cl − , K + , and NO 3 − were accumulated significantly in the cells showing halophilism than that in the salt-untreated cells, and the accumulation of these ions was positively correlated with the growth. Also, the expression of ion homeostasis-related genes for plasma membrane transporters and channels for incorporation of nitrate (McNRT1), sodium (McHKT1), potassium (McKmt1), cations/Cl − (McCCC1), for tonoplast antiporters H + /Cl − (McCLC1) and Na + /H + (McNHX1), and V-ATPase subunit c (McVmac1) for sequestration of Cl − and Na + into the vacuole, and for enzymes catalyzing biosynthesis of proline (McP5CS) and ononitol (McImt1) was higher in the cells showing halophilism than that in the salt-untreated cells. These results indicate that the ion accumulation and the expression of ion homeostasis-related genes contribute to the NaCl-stimulated growth enhancement in the halophyte, the common ice plant. Abbreviations: CCC: cation/Cl-cotransporter; CLC: H+/Cl-antiporter; DW: dry weight; FW: fresh weight; HAK: high affinity potassium; HKT: high potassium transporter; Imt: myo-inositol O-methyl transferase; MIP: major intrinsic protein; NHX: Sodium/proton antiporter; P5CS: delta 1-pyrroline-5-carboxylate synthase; PCV: Packed cell volume; PEG: polyethylene glycol; XTH: xyloglucan endotransglucosylase/ hydrolase The growth enhancement of the ice plants by NaCl was positively correlated with K + accumulation and the increased expression of ion homeostasis related genes contribute to the halophilism. 0 mM 100 mM ARTICLE HISTORY

Transcriptome Analysis of Ice Plant Growth-Promoting Endophytic Bacterium Halomonas sp. Strain MC1 to Identify the Genes Involved in Salt Tolerance

“…Although microbial-mediated drought or heavy metal tolerance in plants [53,54] has been elucidated, our understanding of the salt tolerance mechanisms of EB remains lacking. A recent valuable work has proven that ion accumulation and the expression of ion homeostasis-related genes contribute to the NaCl-stimulated growth enhancement in halophytes, especially the common ice plant [18]. Nevertheless, the current study of Halomonas sp.…”

“…The analysis of novel gene responses of EB may provide a potential method to cope with salinity. EB can enhance Arabidopsis thaliana growth under salt stress and can tolerate high salt concentrations and show a potential competitive advantage of surviving in saline soils [18,19]. The complete genome sequence of the endophyte Bacillus flexus helps in revealing the plant growth-promoting mechanism of EB [20].…”

Adaptive Mechanisms of Halophytes and Their Potential in Improving Salinity Tolerance in Plants

“… Putative salt tolerance mechanisms in an ideal halophyte plant (modified from Zhao et al [ 11 ], Arif et al [ 34 ], Arbelet-Bonnin et al [ 72 ], Tran et al [ 75 ], and Himabindu et al [ 76 ]. The absorption of Na + in plant cells is counterbalanced by active Na + extrusion through SOS1 Na + /H + exchanger ( I ).…”

Ecophysiology and Uses of Halophytes in Diverse Habitats

“…On the other hand, factors that contribute to halophilism include ion (Na + , Cl À , K + , and NO 3À ) accumulation. Tran et al (2020) have observed significant accumulations of these ions in the cells of these plants (halophilism) that do not appear in cells without salt treatment. The accumulation of these ions was positively correlated with the growth.…”