Lamin-like Proteins Negatively Regulate Plant Immunity through NAC WITH TRANSMEMBRANE MOTIF1-LIKE9 and NONEXPRESSOR OF PR 3ENES1 in Arabidopsis thaliana

Nuclear lamins are involved in multiple biological processes in metazoan cells. The proteins of the CROWDED NUCLEI （CRWN） family are considered lamin-like candidates in Arabidopsis, although the functions of these proteins are largely unknown. In this article we show that crwnl crwn2 double mutant displays an enhanced resistance against virulent bacterial pathogens, and both virulent bacteria and salicylic acid （SA） induce transcription of CRWN1 gene as well as proteasome-mediated degradation of CRWN1 protein. We also show that CRWN1 interacts with NAC WITH TRANSMEMBRANE MOTIF1 -LIKE9 （NTL9）, a NAC transcription factor involved in plant immunity. The interaction between CRWN1 and NTL9 enhances the binding of NTL9 to the promoter of the PATHOGENESIS-RELATED1 （PR1） gene, and inhibits PR1 expression. Further genetic experiments indicated that the defense-related phenotypes of crwnl crwn2 double mutant are dependent on NONEXPRESSOR OF PR GENES1 （NPR1）, a transcriptional cofactor of PRI. These findings revealed a regulatory network composed of lamin-like protein CRWN1, NTL9, and NPR1 for the regulation of PR1 expression.

Histone 3 lysine 36 to methionine mutations stably interact with and sequester SDG8 in Arabidopsis thaliana

Post-transcriptional modifications of histones play important roles in various biological processes. Here, we report that Arabidopsis plants overexpressing histone H3 lysine to methionine mutations at histone H3.1K36(H3.1K36M) and H3.3K36(H3.3K36M) have serious developmental defects with early-flowering and change in the modifications of endogenous histone H3, including acetylation at lysine 9(H3K9ac), trimethylation at lysine 27(H3K27me3), di-and tri-methylation at lysine 36(H3K36me2 and H3K36me3). In addition, H3K36M mutation alters its subcellular localization and interacts with H3K36 methyltransferase SDG8. Our results support a model in which H3K36M stably interacts with SDG8, and inhibits the activity of SDG8 by sequestering SDG8, resulting in a dominant negative effect to affect the proper expression levels of a variety of genes and plant development.

Histone variants:making structurally and functionally divergent nucleosomes and linkers in chromatin

In addition to the post-translational modifications of histone proteins,emerging literature suggests that the mosaic nucleosomes formed by incorporation of various histone variants provide another mechanism for modifying chromatin structure and function.The locally defined chromatin by histone variants is involved in transcriptional regulation,DNA repair,centromere packaging,maintenance of pericentromeric heterochromatin,stress responses,temperature sensing,development,and many other biological processes.Here,we review the universal histone variants in H2A,H3 and H1 families and their roles in epigenetics.