Department of Soil Microbiology and Symbiotic Systems, Estaci�n Experimental del Zaid�n (EEZ), CSIC, Calle Profesor Albareda No 1, Granada 18008, Spain.
Noble Research Institute LLC, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA.
Plant Cell Physiol. 2021 May 11;62(2):306-320. doi: 10.1093/pcp/pcaa159.
The formation of arbuscular mycorrhizal (AM) symbiosis requires plant root host cells to undergo major structural and functional reprogramming to house the highly branched AM fungal structure for the reciprocal exchange of nutrients. These morphological modifications are associated with cytoskeleton remodelling. However, molecular bases and the role of microtubules (MTs) and actin filament dynamics during AM formation are largely unknown. In this study, the tomato tsb (tomato similar to SB401) gene, belonging to a Solanaceae group of genes encoding MT-associated proteins (MAPs) for pollen development, was found to be highly expressed in root cells containing arbuscules. At earlier stages of mycorrhizal development, tsb overexpression enhanced the formation of highly developed and transcriptionally active arbuscules, while tsb silencing hampers the formation of mature arbuscules and represses arbuscule functionality. However, at later stages of mycorrhizal colonization, tsb overexpressing (OE) roots accumulate fully developed transcriptionally inactive arbuscules, suggesting that the collapse and turnover of arbuscules might be impaired by TSB accumulation. Imaging analysis of the MT cytoskeleton in cortex root cells OE tsb revealed that TSB is involved in MT bundling. Taken together, our results provide unprecedented insights into the role of novel MAP in MT rearrangements throughout the different stages of the arbuscule life cycle.
丛枝菌根（AM）共生的形成要求植物根系宿主细胞经历重大的结构和功能重编程，以容纳高度分支的 AM 真菌结构，用于养分的互惠交换。这些形态学修饰与细胞骨架重塑有关。然而，AM 形成过程中微管（MTs）和肌动蛋白丝动力学的分子基础和作用在很大程度上尚不清楚。在这项研究中，发现属于茄科编码花粉发育相关 MT 相关蛋白（MAP）的基因家族的番茄 tsb（类似于 SB401 的番茄）基因在含有丛枝的根细胞中高度表达。在共生发育的早期阶段，tsb 过表达增强了高度发达和转录活跃的丛枝的形成，而 tsb 沉默则阻碍了成熟丛枝的形成并抑制了丛枝的功能。然而，在共生定植的后期阶段，tsb 过表达（OE）的根积累了完全发育但转录不活跃的丛枝，表明 TSB 积累可能损害了丛枝的崩溃和周转。对 OE tsb 的皮层根细胞 MT 细胞骨架的成像分析表明，TSB 参与 MT 束的形成。总之，我们的研究结果提供了前所未有的见解，揭示了新型 MAP 在丛枝生命周期的不同阶段 MT 重排中的作用。
