Screening and Expression Analysis of Temperature-responsing Proteins that Can Remove Low Temperature Stagnancy of Seeds Germination of Lepidium apetalum

As a kind of ephemeral plant, Lepidium apetalum Willd. in northern XinJiang shows special responsible characteristics to temperature during the germination: low temperature stratification could improve germination rate and homogeneity of L.apetalum seeds. But it could not germinate and be at stagnation stage under 4 °C , while this phenomenon could be removed by the treatment with 25 °C  for 45 minutes or longer time. The mechanism why the treatment by higher temperature for a short time could remove germination stagnation under low temperature is not clear yet. In this study, the total proteins difference of seeds with three treatments were analyzed by2-DE, which the seeds were without stratification, stayed at germination stagnation stage under low temperature and removed stagnation with 25℃treatment. Screened proteins responsing to temperature which were related to remove germination stagnation under low temperature, and the corresponding genes expression were confirmed by qRT-PCR. The result showed that there was no obvious difference between the seeds without stratification and the seeds at germination stagnation stage by low temperature. But the proteins expression was quite different between the seeds treated with 25 °C  for 45 minutes to remove the germination stagnation and the other two treated samples. 37 distinct protein spots were found in the 2-DE map with 14 up-regulated spots, 23 down-regulated spots. Among them, 6 up-regulated proteins of 14 spots were identified by LC-MS/MS, CDC48E , HSP17.6 and PER12  were further chosen to be confirmed expression analysis by qRT-PCR.The result showed that their relative expression levels were significantly higher in seeds removed stagnation than in seeds before breaking stagnation. In addition, their expression levels were obviously increased with the time prolonging treated by 25 °C  with the highest level with the dealt for 45-55 min and then maintaining this level of expression. The result showed that the genes expression levels were positively correlated to the germination percentage treated with 25 °C  from 30-60 minutes. All the above suggested that Cdc48E, Hsp17.6, and Per12 induced by 25 °C  might be related to the germination stagnation removing of the seeds of L.apetalum . This conclusion provides a new clue for the study on the signal response to temperature in plants.