Guanine- 5-carboxylcytosine base pairs mimic mismatches during DNA replication

The genetic information encoded in genomes must be faithfully replicated and transmitted to daughter cells. The recent discovery of consecutive DNA conversions by TET family proteins of 5-methylcytosine into 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxylcytosine (5caC) suggests these modified cytosines act as DNA lesions, which could threaten genome integrity. Here, we have shown that although 5caC pairs with guanine during DNA replication in vitro, G·5caC pairs stimulated DNA polymerase exonuclease activity and were recognized by the mismatch repair (MMR) proteins. Knockdown of thymine DNA glycosylase increased 5caC in genome, affected cell proliferation via MMR, indicating MMR is a novel reader for 5caC. These results suggest the epigenetic modification products of 5caC behave as DNA lesions

Absorption and distribution of Na+ and some ions in seedlings of Metroxylon vitiense H. Wendl. ex Benth. and Hook. F. under salt stress

Na+, K+, Ca2+, Mg2+ and Cl- concentrations in different plant parts and some physiological characteristics under NaCl treatment in solution culture were determined to investigate the salt resistance of Metroxylon vitiense (H. Wendl.) H. Wendl. ex Benth. & Hook. f. that belongs to the same genus as sago palm (M. sagu Rottb.). Seedlings at the 11th to 13th leaf stages were used for the treatment of 342mM (2%) NaCl for 31 days in a phytotron at 30°C and 75% relative humidity under natural sunlight in mid-summer in central Japan. The Na+ and Cl- concentrations increased in the roots, petioles and leaflets with the NaCl treatment, while, the K+ concentration did not change in the top parts. The Ca2+ and Mg2+ concentrations increased in the leaflets, especially at lower and higher leaf positions, respectively. Leaf emergence and dry matter weight of the top parts were not affected by the NaCl treatment, whereas the transpiration rate decreased. It was, therefore, considered that salt avoidance to maintain the water status in the leaves by restricting the transpiration is important for the salt resistance of M. vitiense. The changes in the Ca2+ concentration can be considered to play a role in adequate absorption of K+, which would enable the plant to maintain osmotic adjustment in the leaflets