Microtubule-associated ROP interactors both delimit and transduce ROP signaling and regulate microtubule dynamics

Abstract

Evidence suggests that ICR proteins function as adaptors that mediate ROP signaling. Here, we studied the functions of ICR2 and its homologs ICR5 and ICR3. We showed that ICR2 is a microtubule-associated protein that regulates microtubule dynamics. ICR2 can retrieve activated ROPs from the plasma membrane, and it is recruited to a subset of ROP domains. Secondary cell wall pits in the metaxylem of icr2 and icr5 Arabidopsis single mutants and icr2/icr5 double and icr2/icr5/icr3 triple mutants were denser and larger than those in wild-type Col-0 seedlings, implicating these three ICRs in restriction of ROP function. The icr2 but not the icr5 mutants developed split root hairs further implicating ICR2 in restriction of ROP signaling. Taken together, our results show that ICR2, and likely also ICR5 and ICR3, have multiple functions as ROP effectors and as regulators of microtubule dynamics.

ROP GTPase‐dependent polarity establishment during tip growth in plants

“…In another report, no redundancy was observed between ICR2, ICR5, and ICR3. Instead, the loss of function of ICR2 alone induced branched root hairs, implying a specific role of ICR2 in restricting the growth point (Feiguelman et al ., 2021). ICR2 is a microtubule‐associated protein and has been proposed to recruit ROPs from membrane to microtubules, thus restricting their localization (Feiguelman et al ., 2021).…”

“…Instead, the loss of function of ICR2 alone induced branched root hairs, implying a specific role of ICR2 in restricting the growth point (Feiguelman et al ., 2021). ICR2 is a microtubule‐associated protein and has been proposed to recruit ROPs from membrane to microtubules, thus restricting their localization (Feiguelman et al ., 2021). ICRs seem to be absent in nonvascular plants, as no homologs are found in Physcomitrium or Selaginella (Eklund et al ., 2010).…”