Component of SUN-protein-containing multivariate complexes also called LINC complexes which link the nucleoskeleton and cytoskeleton by providing versatile outer nuclear membrane attachment sites for cytoskeletal filaments (PubMed:24667841, PubMed:25759303). Required for the maintenance and/or formation of polarized nuclear shape in root hairs (PubMed:21294795, PubMed:25759303). Modulates the anchoring and mobility of WIP proteins and RANGAP1 in the nuclear envelope (NE) (PubMed:22270916). In association with SUN2, may be involved in telomere attachment to nuclear envelope in the prophase of meiosis (PubMed:25412930). As component of the SUN-WIP-WIT2-KAKU1 complex, mediates the transfer of cytoplasmic forces to the nuclear envelope (NE), leading to nuclear shape changes (PubMed:25759303). Forms homomers (e.g. dimers, trimers and tetramers) and heteromers with SUN2 (PubMed:19807882, PubMed:25217773). Interacts with SUN3, SUN4 and TIK (PubMed:25217773). Core component of the LINC complex which is composed of inner nuclear membrane SUN domain-containing proteins coupled to outer nuclear membrane WIP and WIT proteins. The LINC complex also involves nucleoskeletal proteins CRWN/LINC and possibly KAKU4 and the cytoskeletal myosin KAKU1 (PubMed:25759303). Interacts with LINC1, WIP1, WIP2 and WIP3 at the nuclear envelope (NE) (PubMed:22270916, PubMed:24667841). Interacts with SINE1, SINE2, SINE3 AND SINE4 (PubMed:24891605). Interacts with NEAP1, NEA2 and NEAP3 (PubMed:27630107). Dynamic localization during mitosis and meosis, tightly coupled with nuclear envelope (NE) dynamics. Localized with the nuclear envelope during meiotic prophase I. NE re-formation during metaphase is temporally and spatially coordinated with plant-specific microtubule structures such as phragmoplasts. During anaphase, after NE breakdown (NEBD), predominantly localized with the endoplasmic reticulum, in the outside of the segregated chromosomes and not in between segregated chromosomes. Expressed in roots, hypocotyls, cotyledons and leaves and inflorescences. The SUN domain may play a role in nuclear anchoring and/or migration (By similarity). The SUN domain is required for interactions with WIP proteins (PubMed:22270916). No visible phenotype. When associated with SUN2 disruption, abnormal nuclear shape, rounded instead of elongated, in some cells (e.g. mature root hairs) but also numerous meiotic defects namely a delay in the progression of meiosis, absence of full synapsis and a reduction in the mean cell chiasma frequency.