CLASP Interacts with Sorting Nexin 1 to Link Microtubules and Auxin Transport via PIN2 Recycling in Arabidopsis thaliana

Abstract

Polarized movement of auxin generates concentration gradients within plant tissues to control cell division patterns and growth direction by modulating microtubule organization. In this study, we identify a reverse mechanism, wherein microtubules influence polar auxin transport. We show that the microtubule-associated protein CLASP interacts with the retromer component sorting nexin 1 (SNX1) to mediate an association between endosomes and microtubules. clasp-1 null mutants display aberrant SNX1 endosomes, as do wild-type plants treated with microtubule-depolymerizing drugs. Consistent with SNX1's role in trafficking of the auxin efflux carrier PIN-FORMED2 (PIN2), clasp-1 mutant plants have enhanced PIN2 degradation, and PIN2 movement to lytic vacuoles is rapidly induced by depolymerization of microtubules. clasp-1 mutants display aberrant auxin distribution and exhibit numerous auxin-related phenotypes. In addition to mechanistically linking auxin transport and microtubules, our data identify a ubiquitous endosome-microtubule association in plants.

SORTING NEXIN1 Is Required for Modulating the Trafficking and Stability of the Arabidopsis IRON-REGULATED TRANSPORTER1

“…In the absence of Vps5p, the transporter is targeted to the vacuoles (Strochlic et al, 2007). In Arabidopsis, in the absence of SNX1, an enhanced vacuolar localization and degradation of the auxin efflux carrier PIN2 was observed after gravitropic stimulation (Kleine-Vehn et al, 2008;Ambrose et al, 2013). It is important to note that these PIN2 data suggest that SNX1 might also act as a part of the retromer judging from the similar PIN2 localization phenotypes in snx1 and core retromer mutant lines.…”

“…In Arabidopsis, the family contains three members: SNX1, SNX2a, and SNX2b (Vanoosthuyse et al, 2003;Zelazny et al, 2012). SNX1 is a marker for the plant sorting endosome (Jaillais et al, 2008) and was shown to regulate the trafficking of the auxin carrier PIN-FORMED2 (Jaillais et al, 2006;Kleine-Vehn et al, 2008;Ambrose et al, 2013). In the absence of SNX1, the ability of SNX2a or SNX2b to bind the endosomal membrane is abolished; thus, SNX-related defects are observed even in the single snx1 mutant (Pourcher et al, 2010).…”

Rice actin-binding protein RMD is a key link in the auxin–actin regulatory loop that controls cell growth

“…On the other hand, a microtubleassociated protein, CLASP, was shown to connect microtubule arrays with auxin transport by affecting PIN2 trafficking in Arabidopsis (34). Given that RMD directly binds to and bundles microtubules and that rmd mutants display abnormal microtubule arrays (22), a future research direction would be to address whether RMD modulates auxin transport by changing microtubule organization.…”

The dynamics of plant plasma membrane proteins: PINs and beyond

“…In particular, the SORTING NEXIN 1 (SNX1) and VACUOLAR PROTEIN SORTING 29 (VPS29) subunits of the complex have been implicated in PIN recycling (Jaillais et al, 2006(Jaillais et al, , 2007. In mechanistic terms, SNX1 endosomes appear to be recruited to microtubules by direct interaction between retromer and microtubule-associated CLASP, which has been suggested to control cargo recycling to the plasma membrane (Ambrose et al, 2013). SNX1, in particular, appears to control variations in PIN2 degradation in gravistimulated roots and mediates PIN2 retrieval from late endosomes in response to increased temperature, thus linking retromer activity to adaptive growth responses (Jaillais et al, 2006;Kleine-Vehn et al, 2008a;Hanzawa et al, 2013).…”