The Study Of Salt-secreting Mechanisms Underlying Reaumuria Soongorica In Response To Salt And Drought

Salt glands are specialized structure in salt-secretion plant, in which Na~+ efflux is to maintain plant regular physiological process under salinity. Hence salt-secreting plays important roles in plant adaptation to abiotic stress. Reaumuria soongorica, a super xerophytic salt-secretion plant, can maintain low level of Na~+ in plant and alleviate Na~+ toxity to improve its stress resistance by salt-secretion. It’s still unclear about the salt-secreting mechanisms. Na~+/H~+ antiporter in plant plays an important role in mediating cell Na~+ efflux in root and Na~+ compartmentalization in vacules. However, very little is known about Na~+/H~+ antiporter in mediating salt-secretion.For that reason, we choose R. soongorica as research materials, and apply Non-invasive microtest technology(NMT) to analyse the real-time salt-secretion dynamics under salt or osmotic stress. And on this basis the genes encoding the plasma membrane and tonoplast Na~+/H~+ antiporter were cloned from R. soongorica and the expression patterns of genes under salt or osmotic stress were analyzed by real-time PCR. The main results were as follows:(1) Many salt glands, in which cytoplasm is thick, are distributed deep on the leaf epidermis of R. soongorica. R. soongorica is strong salt tolerant, because Na~+ efflux of salt glands can reduce Na~+ concentration in plant, and improve osmotic adjustment ability to maintain plant normal growth under saline enviroment.(2) Both salt and omostic stress can significantly induce net Na~+ efflux and H~+ influx of salt glands of R. soongorica. Moreover, sodium orthvanadate as H~+-ATPase specific inhabitor can significantly reduce net Na~+ efflux and H~+ influx. It demonstrates there is a Na~+/H~+ exchange in salt-secretion.(3) RsSOS1 consisted of 1144 amino acid residues which shared high homology(above 64 %) with reported SOS1 of other plants. RsSOS1 was mainly expressed in shoots, and was induced significantly by salt(50 and 200 mmol·L-1 NaCl) and osmotic(-0.5 and-1.0 MPa) stress condition. The results indicate that RsSOS1 may beinvolved in salt-secretion in R. soongorica, the expression of RsSOS1 was up-regulated rapidly by mediating Na~+ efflux of salt glands under saline environment.(4) The segment of RsNHX1 consisted of 312 amino acid residues which shared high homology(above 77 %) with the identified NHX1 from other plants. RsNHX1 was mainly expressed in shoots, and was induced significantly by salt(50 and 200 mmol·L-1 NaCl) and osmotic(-0.5 and-1.0 MPa) stress condition. The results indicate that RsNHX1 may be involved in salt-secretion in R. soongorica, the expression of RsNHX1 was up-regulated rapidly by mediating Na~+ compartmentalization in vaculor under salinity.