Physiology Indexes Determination And Gene Expression Analysis After Salt Stress In Suaeda Salsa Seed Germination

Suaeda salsa belonging to Suaeda of Chenopodiaceae, is an annual herb halophytewith typical morphological and structural characteristics, the soil which contains highlevels of sodium ions and chloride ions, sulfate ions or combination of carbonate ionswere useful to their growth. Seed germination is an important event in the process ofplant life, plants were most vulnerable to environmental stress in the stage.Suaeda salsa seed, harvested from Hetao Irrigation District in Inner Mongolia wereused throughout this study. The study was carried out to determine influence of salt onseeds germination and physiological index, germinating seeds were treated with variousconcentrations of NaCl （neutral salt） and Na₂CO₃（basic salt）. The differential expressionof genes had been analyzed by cDNA-AFLP in a halophyte Suaeda salsa seedgermination in response to100mmol/L NaCl（the limited NaCl）stress. Details of thestudy were as follow:1. Analyzing effects of different salt on germination characteristics of Suaeda salsaseeds. The result showed that seed germination rate decreased with the increase of saltconcentration and there was significant negative correlation between germination rateand salt concentration, the optimal germination rate of Suaeda salsa seeds was obtainedin distilled water. The correlation coefficient were0.9206between seeds germinationrate of Suaeda salsa and neutral salt （NaCl）, and were and0.9148between seedsgermination rate of Suaeda salsa and basic salt （Na₂CO₃）. The inhibition of Na₂CO₃onseed germination was stronger than NaCl. Limit value of NaCl concentration in Suaedasalsa seed germination was100mmol/L.2. Analyzing variation trend of substances of physiological and biochemical indexrelated to salt tolerance in Suaeda salsa seeds during germination. The results showedsoluble protein change more gentle, SOD first decreased, then increased and lastdecreased, POD, MDA, soluble sugar and content of free proline gradually increasedafter100mmol/L NaCl and Na₂CO₃stress for0,12,24,36,48and60hours. The results further proved that germinating seed of Suaeda salsa had strong tolerance under the stressof NaCl than Na₂CO₃.3. Analyzing genes expression during seeds germination of Suaeda salsa bycDNA-AFLP technique after100mmol/L NaCl stress for0,12,24,36,48and60hours.Differentially expressed fragments were displayed by selective amplification using256primer combinations.851differentially expressed bands were generated, the size of thebands were between100and1000bp. The expression of genes were divided into fiveexpression patterns:“strong�'weak （384,45.1%）”,“weak�'strong （233,27.4%）”,“strong�'weak�'strong （15,1.8%）” and “weak�'strong�'weak （182,21.4%）”,“transient expression （37,4.3%）”.4.113randomly selected transcript derived fragments （TDFs） with differentexpression type were recycled, cloned and sequenced, and their identities were assignedusing the BLASTX searches. The number of genes homology to function-known proteinsaccounted for30%, according to the homology, these TDFs were grouped into sixfunctional categories:“Photosynthesis and energy”（3%）,“Signal transduction”（3%）,“Metabolism”（10%）,“Transduction”（1%）,“Transcription and translation”（1%）,“Defense”（12%）. while the28%of sequences were homologous to genes that codifiedunknown proteins.42%of the TDFs did not show homology to primary amino acidsequences in the databases and were classified as ‘‘No match’’.