Abstract
BackgroundThe movement of plant roots within the soil is key to their ability to interact with the environment and maximize anchorage and nutrient acquisition. Directional growth of roots occurs by a combination of sensing external cues, hormonal signaling and cytoskeletal changes in the root cells. Roots growing on slanted, impenetrable growth medium display a characteristic waving and skewing, and mutants with deviations in these phenotypes assist in identifying genes required for root movement. Our study identifies a role for a trans-Golgi network-localized protein in root skewing.ResultsWe found that Arabidopsis thaliana TNO1 (TGN-localized SYP41-interacting protein), a putative tethering factor localized at the trans-Golgi network, affects root skewing. tno1 knockout mutants display enhanced root skewing and epidermal cell file rotation. Skewing of tno1 roots increases upon microtubule stabilization, but is insensitive to microtubule destabilization. Microtubule destabilization leads to severe defects in cell morphology in tno1 seedlings. Microtubule array orientation is unaffected in the mutant roots, suggesting that the increase in cell file rotation is independent of the orientation of microtubule arrays.ConclusionsWe conclude that TNO1 modulates root skewing in a mechanism that is dependent on microtubules but is not linked to disruption of the orientation of microtubule arrays. In addition, TNO1 is required for maintenance of cell morphology in mature regions of roots and the base of hypocotyls. The TGN-localized SNARE machinery might therefore be important for appropriate epidermal cell file rotation and cell expansion during root growth.
Highlights
The movement of plant roots within the soil is key to their ability to interact with the environment and maximize anchorage and nutrient acquisition
We report here that TGN-localized SYP41-interacting protein (TNO1) acts as a negative regulator of root skewing, since tno1 mutant roots have enhanced skewing which correlates with an enhanced cell file rotation (CFR)
Loss of TNO1 results in exaggerated root skewing Mutants lacking TNO1 have normal root elongation, but show a lag in root gravitropic bending upon gravistimulation [36]
Summary
The movement of plant roots within the soil is key to their ability to interact with the environment and maximize anchorage and nutrient acquisition. Root development and architecture are well-studied [1] but our understanding of how roots interact with soil components is still incomplete. Root growth into the substratum presents multiple cues to the root tip such as mechanical obstacles, moisture and nutrient gradients. These cues are integrated and signal downstream processes involving hormonal pathways and cell expansion [4]. This leads to a cumulative physiological response driving root movement and establishing the root architecture
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