Maize (Zea mays L.) nucleoskeletal proteins regulate nuclear envelope remodeling and function in stomatal complex development and pollen viability

Abstract

In eukaryotes, the nuclear envelope (NE) encloses chromatin and separates it from the rest of the cell. The Linker of Nucleoskeleton and Cytoskeleton (LINC) complex physically bridges across the NE, linking nuclear and cytoplasmic components. In plants, these LINC complexes are beginning to be ascribed roles in cellular and nuclear functions, including chromatin organization, regulation of nuclei shape and movement, and cell division. Homologs of core LINC components, KASH and SUN proteins, have previously been identified in maize. Here, we characterized the presumed LINC-associated maize nucleoskeletal proteins NCH1 and NCH2, homologs of members of the plant NMCP/CRWN family, and MKAKU41, homologous to AtKAKU4. All three proteins localized to the nuclear periphery when transiently and heterologously expressed as fluorescent protein fusions in Nicotiana benthamiana. Overexpression of MKAKU41 caused dramatic changes in the organization of the nuclear periphery, including nuclear invaginations that stained positive for non-nucleoplasmic markers of the inner and outer NE, and the ER. The severity of these invaginations was altered by changes in LINC connections and the actin cytoskeleton. In maize, MKAKU41 appeared to share genetic functions with other LINC components, including control of nuclei shape, stomatal complex development, and pollen viability. Overall, our data show that NCH1, NCH2, and MKAKU41 have characteristic properties of LINC-associated plant nucleoskeletal proteins, including interactions with NE components suggestive of functions at the nuclear periphery that impact the overall nuclear architecture.

A glossary of plant cell structures: Current insights and future questions

“…KAKU4), which bear no sequence homology with animal lamin proteins. These proteins are required for proper nuclear morphology (Wang et al, 2013;Goto et al, 2014;McKenna et al, 2021) and potentially interact extensively with the nuclear pore complex basket (Mermet et al, 2021) and membrane-bound inner nuclear membrane proteins to form the plant nuclear lamina. CRWNs were recently shown to also interact with histone modifiers and to be necessary for tethering chromatin to the inner nuclear membrane to suppress stress-related gene expression (Hu et al, 2019;Mikulski et al, 2019;Choi and Richards, 2020;Sakamoto et al, 2020;Wang et al, 2021).…”

Subcellular positioning during cell division and cell plate formation in maize

“…Nuclear migration is partially dependent on the interaction of actin with a protein in the linker of nucleoskeleton and cytoskeleton (LINC) complex in A. thaliana called SINE2 and in maize called MAIZE LINC KASH SINE-LIKE2 (MLKS2) (Gumber et al, 2019b), (Zhou et al, 2014). In maize, mlks2 mutants have asymmetric division defects (McKenna et al, 2021) due to defective nuclear positioning that causes defects in PPB positioning (Arif Ashraf et al, 2022). A typical live cell marker used to explore nuclear dynamics and chromosome movement in A. thaliana is HISTONE2B fused to Yellow Fluorescent Protein (H2B:YFP) (Boisnard-Lorig et al, 2001).…”