Brassinosteroid signaling delimits root gravitropism via sorting of the Arabidopsis PIN2 auxin transporter

Abstract

Arabidopsis PIN2 protein directs transport of the phytohormone auxin from the root tip into the root elongation zone. Variation in hormone transport, which depends on a delicate interplay between PIN2 sorting to and from polar plasma membrane domains, determines root growth. By employing a constitutively degraded version of PIN2, we identify brassinolides as antagonists of PIN2 endocytosis. This response does not require de novo protein synthesis, but involves early events in canonical brassinolide signaling. Brassinolide-controlled adjustments in PIN2 sorting and intracellular distribution governs formation of a lateral PIN2 gradient in gravistimulated roots, coinciding with adjustments in auxin signaling and directional root growth. Strikingly, simulations indicate that PIN2 gradient formation is no prerequisite for root bending but rather dampens asymmetric auxin flow and signaling. Crosstalk between brassinolide signaling and endocytic PIN2 sorting, thus, appears essential for determining the rate of gravity-induced root curvature via attenuation of differential cell elongation.

Strigolactones inhibit auxin feedback on PIN-dependent auxin transport canalization

“…Notably, auxin itself appears to inhibit the process of endocytosis and antagonize the BFA effect on PIN recycling 15 . In addition to auxin effects on PINs, various other plant hormones can influence PIN-dependent auxin transport, such as cytokinins 23 , brassinosteroids 24,25 , gibberellins 26 , salicylic acid 27 , abscisic acid 28 , and strigolactones (SLs) 29 . However, much remains to be uncovered about the modes of action, by which these plant hormones regulate PINs, thereby ultimately defining plant development.…”

Metabolomic and transcriptomic analyses reveal the regulation of pigmentation in the purple variety of Dendrobium officinale

“…Some studies have indicated that exogenous BR could stimulate the biosynthesis of flavonoids in leaves 52 . Moreover, brassinolide signaling has been implicated in PIN2 sorting and intracellular distribution to delimit root gravitropism 53 . Our transcriptomic data identified the “response to brassinosteroid” and “lipid and wax metabolism” GO terms, and the endogenous brassinolide contents were increased in Pr compared to CK (Fig.…”

Gravity Signaling in Flowering Plant Roots

“…This process is exacerbated by increased auxin-dependent production of small signaling peptides GOLVEN1 ( GLV1) and GLV2 by cells on the lower side, which trigger a response pathway that also favors PIN2 association with the plasma membrane [ 99 ]. Furthermore, other phytohormones, such as the brassinosteroids and gibberellic acid, also function as antagonists of PIN endocytosis [ 100 ]. On the other hand, a long period of exposure to higher auxin levels triggers vacuolar sorting of the PIN2 protein and its vacuolar degradation, thereby potentially contributing to gradient dissipation at the end of a gravitropic response [ 66 ].…”

“…On the other hand, a long period of exposure to higher auxin levels triggers vacuolar sorting of the PIN2 protein and its vacuolar degradation, thereby potentially contributing to gradient dissipation at the end of a gravitropic response [ 66 ]. Hence, a complex crosstalk between hormonal signaling and PIN2 endocytic sorting contributes to regulating root gravitropic curvature [ 100 ].…”