TANGLED1 mediates microtubule interactions that may promote division plane positioning in maize

Abstract

The microtubule cytoskeleton serves as a dynamic structural framework for mitosis in eukaryotic cells. TANGLED1 (TAN1) is a microtubule-binding protein that localizes to the division site and mitotic microtubules and plays a critical role in division plane orientation in plants. Here, in vitro experiments demonstrate that TAN1 directly binds microtubules, mediating microtubule zippering or end-on microtubule interactions, depending on their contact angle. Maize tan1 mutant cells improperly position the preprophase band (PPB), which predicts the future division site. However, cell shape–based modeling indicates that PPB positioning defects are likely a consequence of abnormal cell shapes and not due to TAN1 absence. In telophase, colocalization of growing microtubules ends from the phragmoplast with TAN1 at the division site suggests that TAN1 interacts with microtubule tips end-on. Together, our results suggest that TAN1 contributes to microtubule organization to ensure proper division plane orientation.

Cell cortex microtubules contribute to division plane positioning during telophase in maize

“…Together, this suggests that TAN1 or other division-site localized proteins in close proximity, may promote cortical telophase microtubule plus-end pausing. This microtubule interaction is consistent with in vitro dynamic assays where TAN1 transiently crosslinked microtubules (13).…”

“…TAN1, a microtubule-binding protein that localizes to the division site, is required for proper phragmoplast guidance to the division site (8,21,22). TAN1 crosslinks and bundles microtubules in vitro and co-localizes with microtubules in vivo (13). We hypothesized that loss of TAN1 from the division site would lead to defects in corticaltelophase microtubule organization.…”

“…Cortical-telophase microtubules paused near TAN1-YFP puncta longer than other regions of the division site. TAN1 forms discrete puncta at the division site during telophase ( Fig.1H) (8,21,23), and transiently crosslinks microtubules in vitro (13). We measured microtubule pause time at the division site.…”

Plant cell divisions: variations from the shortest symmetric path

“…This is the case for TANGLED1 (TAN1) whose location at the CDZ is not maintained after PPB disassembly in pok1pok2 [ 42 ] . TAN1 is a microtubule-associated protein whose loss of function in the maize line tan1 results in strong division orientation defects due to a mismatch between phragmoplast and PPB orientation [ 43 ]. It has been proposed that the interaction between TAN1 at the division site and microtubules at the leading edge of the phragmoplast would maintain its trajectory [ 43 ].…”

“…TAN1 is a microtubule-associated protein whose loss of function in the maize line tan1 results in strong division orientation defects due to a mismatch between phragmoplast and PPB orientation [ 43 ]. It has been proposed that the interaction between TAN1 at the division site and microtubules at the leading edge of the phragmoplast would maintain its trajectory [ 43 ]. In addition to the CDZ, POK2 is also present in the midzone of the expanding phragmoplast and interacts with microtubule cross-linker MAP65-3/PLEIADE, this interaction would stabilize the phragmoplast and favour its rapid expansion toward the division site [ 44 ].…”