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Key messageThe Arabidopsis KASH protein SINE3 is involved in male and female gametophyte development, likely affecting the first post-meiotic mitosis in both cases, and is required for full seed set. AbstractLinker of nucleoskeleton and cytoskeleton (LINC) complexes are protein complexes spanning the inner and outer membranes of the nuclear envelope (NE) and are key players in nuclear movement and positioning. Through their roles in nuclear movement and cytoskeletal reorganization, plant LINC complexes affect processes as diverse as pollen tube rupture and stomatal development and function. KASH proteins are the outer nuclear membrane component of the LINC complex, with conserved C-termini but divergent N-terminal cytoplasmic domains. Of the known Arabidopsis KASH proteins, SUN-INTERACTING NUCLEAR ENVELOPE PROTEIN 3 (SINE3) has not been functionally characterized. Here, we show that SINE3 is expressed at all stages of male and female gametophyte development. It is located at the NE in male and female gametophytes. Loss of SINE3 results in a female-derived seed set defect, withsine3mutant ovules arresting at stage FG1. Pollen viability is also significantly reduced, with microspores arresting prior to pollen mitosis I. In addition, sine3mutants have a minor male meiosis defect, with some tetrads containing more than four spores. Together, these results demonstrate that the KASH protein SINE3 plays a crucial role in male and female gametophyte development, likely affecting the first post-meiotic nuclear division in both cases.
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This content will become publicly available on July 31, 2026
Alternative splicing repurposes the Drosophila mitotic regulator Mud for meiotic functions
Abstract Mud/NuMA/LIN-5 (in flies, vertebrates, and worms) is an evolutionarily conserved protein that regulates the shape and orientation of the mitotic spindle. In vertebrate cells, these functions depend on a C-terminal region called the NuMA-Tip, which (i) mediates interaction with the conserved partner protein LGN (called Pins in flies), (ii) contains a highly conserved subsequence called the NLM, and (ii) binds directly to microtubule ends. Although Mud plays a vital role in Drosophila mitosis, less is known about its structure, particularly at the C-terminus. Through sequence analysis and functional studies, we identify the Mud-Tip region and show that it is encoded by 3 consecutive exons. These exons are spliced out of several Mud isoforms, creating functionally distinct “Tipless” variants. We find that Tipless isoforms are specifically expressed in male and female gametes, where they localize to the nuclear envelope. Although Mud is known to be essential for female fertility, we demonstrate that this function does not require an intact Tip region. We also find that Mud antagonizes the localization of Lamin, a nucleoskeletal protein, in the testis, and uncover an unexpected role for Tipless Mud in promoting male fertility. Our work reveals that while the Mud-Tip is important for Mud function at mitosis, alternative splicing ensures this region is absent from Mud isoforms that perform a moonlighting role during meiosis.
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- Award ID(s):
- 2409495
- PAR ID:
- 10656177
- Editor(s):
- Andrew, D
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- GENETICS
- Volume:
- 231
- Issue:
- 2
- ISSN:
- 1943-2631
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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