Cortical microtubules contribute to division plane positioning during telophase in maize

Abstract

Cell divisions are accurately positioned to generate cells of the correct size and shape. In plant cells, the new cell wall is built in the middle of the cell by vesicles trafficked along an antiparallel microtubule and a microfilament array called the phragmoplast. The phragmoplast expands towards a specific location at the cell cortex called the division site, but how it accurately reaches the division site is unclear. We observed microtubule arrays that accumulate at the cell cortex during the telophase transition in maize (Zea mays) leaf epidermal cells. Before the phragmoplast reaches the cell cortex, these cortical-telophase microtubules transiently interact with the division site. Increased microtubule plus-end capture and pausing occur when microtubules contact the division site-localized protein TANGLED1 or other closely associated proteins. Microtubule capture and pausing align the cortical microtubules perpendicular to the division site during telophase. Once the phragmoplast reaches the cell cortex, cortical-telophase microtubules are incorporated into the phragmoplast primarily by parallel bundling. The addition of microtubules into the phragmoplast promotes fine-tuning of the positioning at the division site. Our hypothesis is that division site-localized proteins such as TANGLED1 organize cortical microtubules during telophase to mediate phragmoplast positioning at the final division plane.

Subcellular positioning during cell division and cell plate formation in maize

“…Similar increased dynamicity is observed in cultured tobacco (BY-2) cells when cells had PPBs (Vos et al, 2004). In addition, faster growth and shrinkage was seen during telophase in maize epidermal cells, similar to previous reports (Bellinger et al, 2023). This increased microtubule dynamicity during mitosis may reflect alterations in the balance of microtubule associated proteins or in the relative amount of tubulin captured in various mitotic structures.…”

De novo TANGLED1 recruitment from the phragmoplast to aberrant cell plate fusion sites in maize

“…The maize tan1 mutant has mostly normally placed PPBs, but phragmoplast guidance defects lead to misoriented symmetric and asymmetric divisions ( Smith et al, 1996 ; Martinez et al, 2017 , 2020 ). TAN1 promotes contact angle-independent microtubule interactions, which guide the phragmoplast to the division site ( Bellinger et al, 2023 ; Martinez et al, 2020 ).…”

Against the grain: Certain microtubules arrange perpendicularly to the division site to guide cell division in maize

“…Recent work by Marschal Bellinger, Aimee Uyehara, and their colleagues ( Bellinger et al 2023 ) reveals more about how the phragmoplast is precisely positioned during cell division in maize. Using live-cell imaging of actively dividing maize epidermal cells, they observed a distinct group of microtubules accumulating during telophase near the cell cortex rather than from or within the phragmoplast.…”

“… Cortical-telophase microtubules aid in guiding the phragmoplast in maize. Bellinger et al (2023) describe a unique population of cortical microtubules that appears during telophase in maize epidermal cells. These extend from the cortex toward the division plane (dashed box) where they often pause and reorient to be perpendicular to the plane.…”