Microtubule organization changes severely after mannitol and n-butanol treatments inducing microspore embryogenesis in bread wheat

19 Pags.- 8 Figs. © The Author(s) 2021. Open Access. This article is licensed under a Creative Commons Attribution 4.0 International License.Background A mannitol stress treatment and a subsequent application of n-butanol, known as a microtubule-disrupting agent, enhance microspore embryogenesis (ME) induction and plant regeneration in bread wheat. To characterize changes in cortical (CMT) and endoplasmic (EMT) microtubules organization and dynamics, associated with ME induction treatments, immunocytochemistry studies complemented by confocal laser scanning microscopy (CLSM) were accomplished. This technique has allowed us to perform advanced 3- and 4D studies of MT architecture. The degree of MT fragmentation was examined by the relative fluorescence intensity quantification. Results In uni-nucleated mannitol-treated microspores, severe CMT and EMT fragmentation occurs, although a complex network of short EMT bundles protected the nucleus. Additional treatment with n-butanol resulted in further depolymerization of both CMT and EMT, simultaneously with the formation of MT aggregates in the perinuclear region. Some aggregates resembled a preprophase band. In addition, a portion of the microspores progressed to the first mitotic division during the treatments. Bi-nucleate pollen-like structures showed a high MT depolymerization after mannitol treatment and numerous EMT bundles around the vegetative and generative nuclei after n-butanol. Interestingly, bi-nucleate symmetric structures showed prominent stabilization of EMT. Conclusions Fragmentation and stabilization of microtubules induced by mannitol- and n-butanol lead to new configurations essential for the induction of microspore embryogenesis in bread wheat. These results provide robust insight into MT dynamics during EM induction and open avenues to address newly targeted treatments to induce ME in recalcitrant species.This work was supported by Projects AGL2010-17509 and AGL2016-77211-R of the State R&D Program Oriented to the Challenges of the Society of Spain, the Bilateral Project CSIC (Spain)-PAS (Poland) 2010PL0006 and COST Action FA0903 ‘Harnessing of Reproduction for Plant Improvement’ (HAPRECI). Dr. Ewa Dubas was the recipient of a STSM fellowship from COST Action FA0903 ‘Harnessing of Reproduction for Plant Improvement’. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).Peer reviewe