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, homologous to 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 membranes, 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.

Characterization of a Plant Nuclear Matrix Constituent Protein in Liverwort

“…We next examined nuclear localization patterns of MpNMCP proteins by immunohistostaining, in which functional MpNMCP:2HA fusion proteins were visualized with fluorophore-conjugated anti-HA antibodies. As shown by representative images in Figure 3A, MpNMCP is preferentially localized at the nuclear periphery in vivo, which is similar to many NMCP proteins from various plants species (Ciska et al, 2013;Sakamoto and Takagi, 2013;Yang et al, 2020;McKenna et al, 2021). Besides, we found that MpNMCP proteins were not evenly distributed at the nuclear periphery but exhibited a punctate-like pattern, which was similar to that from onion (Ciska et al, 2013).…”

“…Additionally, overexpression of Arabidopsis CRWN1 can partially deform the nuclear envelope by forming invaginations (Goto et al, 2014). Similar effects with the maize NMCP homolog, NCH1, have also been reported recently (McKenna et al, 2021). The conserved localization of Marchantia NMCP at the NL prompted us to ask if knocking out MpCRWN would result in similar defects in nuclear morphology and whether these defects would underlie the suppressed growth phenotype seen in the Mpnmcp mutants.…”

“…Early functional characterization of AtCRWN1 unveiled its role in regulating nuclear morphology (Dittmer et al, 2007). Functional studies of other NMCPs have been conducted on multiple plants, including rice (Yang et al, 2020), maize (McKenna et al, 2021), and onion (Ciska et al, 2013); yet it is unknown whether the corresponding NMCP genes in these plants play a structural role in the nucleus. In this study, we showed that although MpNMCP proteins were located at the nuclear periphery (Figure 3A), the Mpnmcp mutant does not show changes in nuclear size or shape (Figures 3B-D).…”

Resolving the Cohenian paradox in judicial probability theory

“…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).…”

The Plant Nuclear Envelope and Its Role in Gene Transcription

“…For example, lamin proteins which represent the major constituents of the animal lamina have not been identified in plants (Meier et al, 2017). Instead, three types of plant-specific proteins, CROWDED NUCLEI (CRWN) or nuclear matrix constituent protein (NMCP), KAKU4 and nuclear envelope-associated proteins (NEAPs) have been suggested to function as lamin-like proteins in plants (Masuda et al, 1997;Ciska and de la Espina, 2014;Goto et al, 2014;Pawar et al, 2016;McKenna et al, 2021). Beyond its scaffolding role, the nuclear lamina is of functional importance in chromatin folding, DNA repair, and gene transcription (Burke and Stewart, 2013).…”