| Sesuvium portulacastrum L. is a kind of succulent herb growing in tropical and subtropical intertidal land. It grows well and finishs life cycle when it is cultivated in both fresh and sea water. In this study, the seedlings of S. portulacastrum watered with fresh water and sea water for 3 months were used as the materials to study their adaptable characteristics in response to salt tolerances, which included morphological structure, mesophyll cell ultrastructure, protein accumulation, the ion micro-distriction and protein expression. In addition, we isolated three STRG152 homologous genes from S. portulacastrum and preliminarily analysis their function in yeast and Arabidopsis. The results are as follows:1. When the plants of S. portulacastrum were watered with sea water, the leaves were thicken, and the leaf epidermal cells consisted of the bubble-like parenchyma cells that were enlarged and bulged from the surface. It is deduced that the main function of these cells was for water-absorbing from outside to reduce the cell osmotic pressure, which they are useful to reduce the salt concentration in plant vivo.2. When the plants of S. portulacastrum were watered with the sea water, the plasma membrane of mesophyll cells were clearly folded inward, and formed many of different sizes and shapes of protrusions and lamellaes in their plasma membrane; However when the plants of S. portulacastrum were cultivated in the fresh water, the folding inward of plasma membrane in mesophyll cells was not so obvious.3. When the plants of S. portulacastrum were watered with sea water, the chloroplasts in mesophyll cells were smaller with shorted shape, but the number of them was increased. The shape of chloroplasts was changed from shapes of kidney, spindle or arciform to ellipse or irregular. The grana lamella of chloroplasts was integrity and clear, and the stacking degree was increased. The chloroplasts had not been significantly hurt. The number of starch grains in chloroplasts was increased, and the size was enlarged. The surface of starch grains appeared wrinkly, and the shape was changed from oblong to short oval or irregular. Electron density was become lower. The number of liposomes on chloroplast was increased, and the size was enlarged. 4. When the plants of S. portulacastrum were watered with sea water, the mitochondria in mesophyll cells were smaller with shorted shape, but the number of them was increased. The shape was changed from the shapes of stick and sphere to ellipse and sphere. The construct of mitochondria was integrity. The mitochondrial cristaes were clear, but the mitochondria membrane was fuzzy and hurt. When the plants of S. portulacastrum were watered with fresh water, the mitochondria were line profile and the mitochondrial cristaes were clear.5. The Na element in the stem was higher than that in leaf of S. portulacastrum when it was watered with fresh water, but Na element in the leaf was higher than that in the stem of S. portulacastrum when it was watered with sea water. Under salt stress, Na element sharply increased in the leaf tissues of epidermal cells, palisade tissue and water organization, and the increasing proportion among them was almost equal. Na element in stem of S. portulacastrum watered with sea water was slightly hgher than that of S. portulacastrum watered with sea water, and the increasing proportion among the stem tissues was higher in the pith cells than epidermal and vascular system.6. The Na+ poison didn’t decrease the absorption of K+ in S. portulacastrum vivo, in contrast to it, the K+ content was increased when the plants were watered with sea water, so they was not hurt because of lacking K+ under salt-stress.7. Under salt stress, the Cl element was much increased in the parts of leaf and stem, in which Na element was increased. Cl element was almost the similar level in vascular system of stem, but the Cl element is higher in pith and epidermal systems when the plants were watered with sea water. It is deduced that Cl element plays a role in cation neutralization; osmotic pressure addition, and leaf succulence.8. When the plants of S. portulacastrum were watered with sea water, the granular materials and membranous materials were increased in the stem parenchyma cells, and protein accumulationwas increased in all tissue of leaf, but not clearly increased in stem.9. With plus or minus 2 fold protein expression as a standard,13.3% down-regulation protein dots, and 15.7% up-regulation dots were observed when the plants of S. portulacastrum were watered with sea water.73 protein dots with plus or minus 2.5 fold protein expressing have been analyzed by Using MALDI-TOF-MS and MALDI-TOF-TOF-MS. These protein dots can be divided into 11 categories. (ⅰ) 8 protein dots belong to stress responses and defense related proteins; (ⅱ) 25 protein dots belonge to photosynthesis related proteins; (ⅲ) 6 protein dots belong to energy metabolism related proteins; (ⅳ)10 protein dots belong to carbohydryate metabolism associated proteins; (ⅴ) 4 protein dots belong to transcription, translation and trafficking; (ⅵ) 4 protein dots belong to detoxifying and antioxidant enzymes; (ⅶ) 6 protein dots belong to signal transduction related proteins; (ⅷ) 2 protein dots belong to cytoskeleton dynamics; (ⅸ) 2 protein dots belong to growth and development related proteins; (ⅹ) 5 protein dots belong to function unknown and hypothetical proteins; (Ⅺ) 1 protein dot belongs to nucleotide acid metabolism protein.10. We cloned tree homologous genes of STRG152 from S. portulacastrum andnamed SRTG152-Ⅰ, SRTG152-Ⅱand SRTG152-Ⅲ(GenBank accession:FJ457924, FJ457925 and FJ457926). We preliminarily analyzed the function of SRTG152-Ⅰgene in Yeast and Arabidopsis. SRTG152-Ⅰgene was preliminarily identified to relate high K+ tolerance. |
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