Effect of Hypermethylation of CCWGG Sequences in DNA of Mesembryanthemum crystallinum Plants on Their Adaptation to Salt Stress

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O. V. Dyachenko¹, N. S. Zakharchenko¹, T. V. Shevchuk¹, H. J. Bohnert², J. C. Cushman³, and Ya. I. Buryanov^1*

¹Branch of Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, pr. Nauki 6, 142290 Pushchino, Moscow Region, Russia; fax: (8-27) 33-0527; E-mail: buryanov@fibkh.serpukhov.su

²Department of Plant Biology, University of Illinois, 1201 West Gregory Drive, Urbana, IL 61801, USA; E-mail: bohnerth@life.uiuc.edu

³Department of Biochemistry, University of Nevada, Reno/MS 200, 1664 North Virginia Street, Reno, Nevada 89557, USA; E-mail: jcushman@unr.edu

^* To whom correspondence should be addressed.

Received November 15, 2005

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Under salt stress conditions, the level of CpNpG-methylation (N is any nucleoside) of the nuclear genome of the facultative halophyte Mesembryanthemum crystallinum in the CCWGG sequences (W = A or T) increases two-fold and is coupled with hypermethylation of satellite DNA on switching-over of C₃-photosynthesis to the crassulacean acid metabolism (CAM) pathway of carbon dioxide assimilation. The methylation pattern of the CCWGG sequences is not changed in both the 5´-promoter region of the gene of phosphoenolpyruvate carboxylase, the key enzyme of C₄-photosynthesis and CAM, and in the nuclear ribosomal DNA. Thus, a specific CpNpG-hypermethylation of satellite DNA has been found under conditions of expression of a new metabolic program. The functional role of the CpNpG-hypermethylation of satellite DNA is probably associated with formation of a specialized chromatin structure simultaneously regulating expression of a large number of genes in the cells of M. crystallinum plants on their adaptation to salt stress and switching-over to CAM metabolism.

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KEY WORDS: Mesembryanthemum crystallinum, salt stress, adaptation, CAM metabolism, DNA, methylation, CpNpG sequences, PEP carboxylase and rRNA genes, satellite DNA

DOI: 10.1134/S000629790604016X

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