Abscisic Acid Regulates the Root Growth Trajectory by Reducing Auxin Transporter PIN2 Protein Levels in Arabidopsis thaliana

Abstract

The root is in direct contact with soil. Modulation of root growth in response to alterations in soil conditions is pivotal for plant adaptation. Extensive research has been conducted concerning the adjustment of root elongation and architecture in response to environmental factors. However, little is known about the modulation of the root growth trajectory, as well as its hormonal mechanism. Here we report that abscisic acid (ABA) participated in controlling root growth trajectory. The roots upon ABA treatment or from ABA-accumulation double mutant cyp707a1,3 exhibit agravitropism-like growth pattern (wavy growth trajectory). The agravitropism-like phenotype is mainly ascribed to the compromised shootward transportation of auxin since we detected a reduced fluorescence intensity of auxin reporter DR5:VENUS in the root epidermis upon exogenous ABA application or in the endogenous ABA-accumulation double mutant cyp707a1,3. We then tried to decipher the mechanism by which ABA suppressed shootward auxin transport. The membrane abundance of PIN2, a facilitator of shootward auxin transport, was significantly reduced following ABA treatment and in cyp707a1,3. Finally, we revealed that ABA reduced the membrane PIN2 intensity through suppressing the PIN2 expression rather than accelerating PIN2 degradation. Ultimately, our results suggest a pivotal role for ABA in the root growth trajectory and the hormonal interactions orchestrating this process.

Roles of abscisic acid in regulating ripening and quality of strawberry, a model non-climacteric fruit

“…As crucial regulators of plant growth and development, interactions between phytohormones occur frequently. Such interactions, often referred to as ‘crosstalk’, without defining any specific mechanisms, have been reported widely [ 12 , 96 – 98 ], e.g. between ABA and other phytohormones, including auxins, gibberellins (GAs), ethylene, and jasmonic acids (JAs) [ 3 , 4 , 7 ].…”

Salicylic Acid Regulates Root Gravitropic Growth via Clathrin-Independent Endocytic Trafficking of PIN2 Auxin Transporter in Arabidopsis thaliana

“…We concluded that by regulating the expression of PIN2 and the degradation of PIN2 protein, high levels of SA impaired PIN2-dependent auxin transport and inhibited root hair growth. Differently, exogenous ABA application reduced the intensity of membrane PIN2 by suppressing PIN2 expression rather than by accelerating PIN2 degradation to elicit the waving root growth trajectory [ 43 ]. At a concentration of 100 μM, SA stimulated PIN2 hyperclustering during gravitropism [ 32 ].…”

Abscisic acid is involved in several processes associated with root system architecture in maize

“…Moreover, PR inhibition by ABA requires intact auxin transport and signalling, whereas LR elongation does not (Emenecker and Strader 2020). The interaction between ABA and auxin in RSA is complex, as auxin polar transport is responsible for auxin movement in plants, and ABA alters the expression of auxin transporters (Brady et al 2003;Sun et al 2018;Xie et al 2021). Moreover, ABA interferes with auxin transport.…”

“…Therefore, these results suggest that auxin works downstream of ABA in root elongation. Recently, it was found that exogenous ABA reduces the expression of PIN2 an auxin transporter (Xie et al 2021).…”