Physiological And Methylation Analysis Of Brassica Napus And Brasssica Oleracea Seed Germination In Response To Saline Stress

Epigenetic regulation plays crucial roles in plants development and response to abiotic-stresses. As two of the important contents in epigenetic research, DNA methylation and histone modification have become the focus of attention in recent studies. Epigenetic regulation is essentially the change and stable inheritance of the genetic material without a change in DNA sequence. Studies show the combination of histone modifications and the information of DNA methylation regulate the structure of chromatin and determine gene expression. To date, levels of DNA and histone methylation change in roots meristematic cell of Brassica napus and B.oleracea seedlings grown under salt stress have been rarely reported.Here, changes of epigenetic modifications including DNA and histone methylation are studied for the purpose of understanding the interaction of chromatin modifications and their roles in stress response under NaCl treatments. Our study will contribute to reveal the functions and genetic mechanism of histone modification and DNA methylation in plant response to salt stress.HPLC-assisted quantification and immunofluorescent staining were carried out to analyze the level and variation patterns of DNA and histone methylation at different time (48 h,60h and 72 h) during Brassica napus L. cv.’Yangyou 9’and B.oleracea cv. ’Zhongjuajielan’seed germination under different concentrations of NaCl (0 mM,25 mM,50 mM and 100 mM). The result of morphological and physiological analysis under salt stress indicated that allotetraploid ’Yangyou 9’ had stronger salt tolerance than diploid ’Zhongjuajielan’. The epigenetic analysis showed that 25 mM NaCl mediated the enrichment of H3K4me3, decrease of H3K9me2 and 5-mC, whereas 50 mM and 100 mM induced increase of H3K9me2 and 5-mC and decrease of H3K4me3. High concentration of NaCl intensified the methylation degree.The levels of DNA methylation in ’Yangyou 9’and ’Zhongjuajielan’under NaCl treatment increased during seed germination. In’Yangyou 9’, the levels of H3K9me2 increased during the whole early germination stage, but H3K4me3 decreased. In contrast to’Yangyou 9’, the levels of’Zhongjuajielan’ H3K9me2 declined during 48 h to 60 h salt treatment, and then increased rapidly to reach a high level from 60 h to 72 h after treatment. The change tendency of H3K4me3 was opposite to that of H3K9me2. In conclusion, the methylation regulation pattern of B.napus cv.’Yangyou 9’ seed germination in response to saline stress is different to B. oleracea cv.’Zhongjuajielan’...