Maize tubulin folding cofactor B is required for cell division and cell growth through modulating microtubule homeostasis

center dot Tubulin folding cofactors (TFCs) are required for tubulin folding, alpha/beta tubulin heterodimer formation, and microtubule (MT) dynamics in yeast and mammals. However, the functions of their plant counterparts remain to be characterized. center dot We identified a natural maize crumpled kernel mutant, crk2, which exhibits reductions in endosperm cell number and size, as well as embryo/seedling lethality. Map-based cloning and functional complementation confirmed that ZmTFCB is causal for the mutation. center dot ZmTFCB is targeted mainly to the cytosol. It facilitates alpha-tubulin folding and heterodimer formation through sequential interactions with the cytosolic chaperonin-containing TCP-1 epsilon subunit ZmCCT5 and ZmTFCE, thus affecting the organization of both the spindle and phragmoplast MT array and the cortical MT polymerization and array formation, which consequently mediated cell division and cell growth. We detected a physical association between ZmTFCB and the maize MT plus-end binding protein END-BINDING1 (ZmEB1), indicating that ZmTFCB1 may modulate MT dynamics by sequestering ZmEB1. center dot Our data demonstrate that ZmTFCB is required for cell division and cell growth through modulating MT homeostasis, an evolutionarily conserved machinery with some species-specific divergence.

Automated summary

This study reveals the crucial role of ZmTFCB, a tubulin folding cofactor, in cell division and cell growth in maize.