Arabidopsis PIC30 encodes a major facilitator superfamily transporter responsible for the uptake of picolinate herbicides

Abstract

Picloram is an auxinic herbicide that is widely used for controlling broad leaf weeds. However, its mechanism of transport into plants is poorly understood. In a genetic screen for picloram resistance, we identified three Arabidopsis mutant alleles of PIC30 (PICLORAM RESISTANT30) that are specifically resistant to picolinates, but not to other auxins. PIC30 is a previously uncharacterized gene that encodes a major facilitator superfamily (MFS) transporter. Similar to most members of MFS, PIC30 contains 12 putative transmembrane domains, and PIC30-GFP fusion protein selectively localizes to the plasma membrane. In planta transport assays demonstrate that PIC30 specifically transports picloram, but not indole-3-acetic acid (IAA). Functional analysis of Xenopus laevis oocytes injected with PIC30 cRNA demonstrated PIC30 mediated transport of picloram and several anions, including nitrate and chloride. Consistent with these roles of PIC30, three allelic pic30 mutants are selectively insensitive to picolinate herbicides, while pic30-3 is also defective in chlorate (analogue of nitrate) transport and also shows reduced uptake of 15 NO À 3 . Overexpression of PIC30 fully complements both picloram and chlorate insensitive phenotypes of pic30-3. Despite the continued use of picloram as an herbicide, a transporter for picloram was not known until now. This work provides insight into the mechanisms of plant resistance to picolinate herbicides and also shed light on the possible endogenous function of PIC30 protein.

PIN3 positively regulates the late initiation of ovule primordia in Arabidopsis thaliana

“…Statistical analysis showed that the ovule number per placenta of the wild-type and pin3 mutants at floral stages 9c-11 wasn't obviously increased under NAA treatment, implying that exogenous NAA did not efficiently enhance the auxin signal that is sufficient to promote ovule initiation, regardless of the presence of a functional PIN3 in the wild-type (S3A-S3C Fig) . Meanwhile, another auxin analogue, picloram was also applied to the wild-type and pin3 mutants. Picloram is transported into cells by a special native plasma membrane-bound influx carrier PIC30, a member of the major facilitator superfamily (MFS) [55,56]. Interestingly, the pistil length and ovule number of the wild-type and pin3 mutants were both significantly increased upon picloram treatment (Fig 5A -5C).…”

“…initiation even in the presence of NAA (S3 Fig) . By contrast, picloram, a synthetic auxin analogue, is absorbed rapidly by a special influx transporter PIC30 and accumulates in growing tissues [55,56]. Thus, the rapid uptake and accumulation of picloram, which is independent with PIN3, may be liable to enhance total auxin signaling and response (Fig 5D -5G).…”

Mining Fiskeby III and Mandarin (Ottawa) Expression Profiles to Understand Iron Stress Tolerant Responses in Soybean

“…Four additional stress-related genes are also up-regulated under FeD conditions. These include Glyma.04G228300, a homolog of AtAPRR5 (At5g24470), which is involved in the SnRK pathway and regulates cytokinin [62]; Glyma.05G145000, a member of the multidrug resistance-associated protein family likely serving as a metal transporter in Arabidopsis (At3g13080) [60]; Glyma.05G169900, encodes a plantacyanin a copper-containing protein involved in tolerance to heavy metal stress tolerance in Arabidopsis (At2g02850) [63]; Glyma.10G276700, a major facilitator known to transport nitrate in Arabidopsis (At2g39210) [64], and Glyma.20G133200, a homolog of AtZAT10. In Arabidopsis, ZAT10 (At1g27730) is strongly induced by ABA and numerous abiotic stresses to provide enhanced stress tolerance [65].…”