Katanin-Dependent Microtubule Ordering in Association with ABA Is Important for Root Hydrotropism

Abstract

Root hydrotropism refers to root directional growth toward soil moisture. Cortical microtubule arrays are essential for determining the growth axis of the elongating cells in plants. However, the role of microtubule reorganization in root hydrotropism remains elusive. Here, we demonstrate that the well-ordered microtubule arrays and the microtubule-severing protein KATANIN (KTN) play important roles in regulating root hydrotropism in Arabidopsis. We found that the root hydrotropic bending of the ktn1 mutant was severely attenuated but not root gravitropism. After hydrostimulation, cortical microtubule arrays in cells of the elongation zone of wild-type (WT) Col-0 roots were reoriented from transverse into an oblique array along the axis of cell elongation, whereas the microtubule arrays in the ktn1 mutant remained in disorder. Moreover, we revealed that abscisic acid (ABA) signaling enhanced the root hydrotropism of WT and partially rescued the oryzalin (a microtubule destabilizer) alterative root hydrotropism of WT but not ktn1 mutants. These results suggest that katanin-dependent microtubule ordering is required for root hydrotropism, which might work downstream of ABA signaling pathways for plant roots to search for water.

Abscisic Acid Inhibits Cortical Microtubules Reorganization and Enhances Ultraviolet-B Tolerance in Arabidopsis thaliana

“…As a universal stress hormone, cellular ABA has been shown to mediate plants’ development [ 15 , 16 , 17 , 30 , 36 , 37 , 38 ]. ABA is synthesized and accumulated in roots and regulates primary root growth in A. thaliana in a concentration-dependent manner, which exogenously applied in low concentrations stimulates, while at high concentrations inhibits root growth [ 16 , 17 ].…”

“…The microtubule cytoskeleton is widely involved in many key processes in plant morphogenesis [ 28 , 40 ] and the response to adverse environments [ 21 , 22 , 23 , 30 ] for the dynamic features, hence microtubule cytoskeletons are believed to perceive signal transduction in plant stress response [ 30 , 41 , 42 , 43 ]. However, the crosstalk and underlying mechanism between microtubules and these signals are still insufficiently studied.…”

“…Therefore our results were consistent with previous reports that plants could harden, and ABA treatment increased the stability of tubulin microtubules and reduced the depolymerized action of oryzalin in winter wheat cultivars [ 46 ]. ABA signaling also partially rescues the oryzalin-induced (a microtubule-specific destabilizer) alternative root hydrotropism of wild-type A. thaliana [ 30 ].…”

“…Plant growth and morphogenesis change due to disturbed microtubule organization in A. thaliana which suffered from UV-B radiation [ 6 , 26 ]. Microtubule reorganization and corresponding morphology caused by stress are connected with cellular signals, such as nitric oxide [ 6 , 24 , 27 ], brassinosteroid [ 28 ], and ABA [ 29 , 30 ]. It is essential to comprehensively investigate the effects of UV-B radiation on plant growth and the relations of hormone signals and microtubule cytoskeleton.…”

Arabidopsis MYB21 Negatively Regulates KTN1 to Fine-Tune the Filament Elongation

“…Microtubule (MT) is a critical constituent of the cellular cytoskeleton, and research has increasingly demonstrated a close relationship between the establishment of cell morphology in plant cells and the cortical MT array and dynamics within the cell [21,22]. KTN1, which encodes a katanin p60 subunit, plays an important role in plant cell morphogenesis [12,[22][23][24][25]. Studies have shown that KTN1 and KTN80 form KTN1-KTN80 heterodimers, which was activated by BZR1-family transcription factors (BFTFs), thereby associated with BRs signaling pathway to precisely perform MT severing and properly regulate filament elongation in Arabidopsis [12,22].…”