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.

Long interspersed element ‐1 (LINE‐1) is a mobile element, or jumping gene, which employs a “copy and paste” method called retrotransposition to insert itself into the human genome. This retrotransposition mechanism utilizes an enzyme called the L1 endonuclease to initiate the double strand breaks necessary for LINE‐1 insertion. Studies have found that a significant portion of the human genome is composed of mobile elements, which have likely played a crucial evolutionary role in the current genetic variability observed in humans. However, in some instances the mutations that have arisen from increased LINE‐1 retrotransposition, have been linked to genetic diseases such as colon cancer, breast cancer, and have been linked to genome instability due to increased double strand breaks. Previous research suggests that heavy metals such as Ni2+, Co2+, and Cd2+, which occur in our industrialized environment as pollutants, potentially affect levels of LINE‐1 retrotransposition. These toxic metals have been observed to compete with Mg2+ as cofactors for proteins, and have been observed to inhibit essential reactions in DNA repair. Competition with Mg as a cofactor suggests these heavy metals likely have an effect on levels of LINE‐1 endonuclease activity in vitro since it also utilizes Mg2+ as a cofactor for enzymatic activity. We focused on the effects that the heavy metals cobalt and cadmium have on the LINE‐1 endonuclease activity to determine whether or not these metals also influence levels of double strand breaks in vitro. Preliminary results indicate that the metal cobalt does not prevent LINE‐1 endonuclease activity at doses up to 100uM.Support or Funding InformationThis work was funded by an Institutional Development Award (IDeA) from the NIGMS under grant number P20GM103424 and from the Louisiana Cancer Research Consortium, the NIH‐RCMI grant #8G12MD007595‐05.

Long interspersed element‐1 (LINE1) is the only currently active autonomous retroelement within the human genome. LINE1 replicates itself through a process known as retrotransposition that requires the endonuclease and reverse transcriptase activities of the LINE1 protein ORF2. During retrotransposition, the LINE1 endonuclease recognizes an AT‐rich target sequence loosely defined as 5'TTTT/AA3' (“/” denotes site of cleavage). After nicking of DNA by LINE1 endonuclease and reverse transcription of LINE1 RNA, a new copy of LINE1 is inserted into the genome. The complete details of LINE1 insertion are undefined, however, a double strand break (DSB) must occur during this process prior to integration of novel LINE1 elements. Further studies characterizing LINE1 endonuclease function demonstrated that LINE1 endonuclease induces formation of DSBs. While LINE1 mutagenic insertion events have been associated with diseases such as breast and colon cancer as well as muscular dystrophy, the full effect of LINE1 endonuclease upon stability of the genome is undetermined. Only a small fraction of LINE1‐induced DSBs results in a retrotransposition event suggesting that the damage from the LINE1 endonuclease activity may be greater than previously considered. Thus, an inhibitor of LINE1 endonuclease would be beneficial for estimating LINE1‐associated damage and to potentially minimize LINE1‐related genetic instability. Methodology: We have performed in vitro and in silico screens of small molecule libraries. The small molecules identified will be confirmed for their ability to inhibit the LINE1 endonuclease using in vitro biochemical assays. Results: We have thus far identified a subset of small molecules that inhibit the LINE1 endonuclease. Grant Funding Source: Supported by funding from the Louisiana Cancer Research Consortium and the NIH‐RCMI grant #8G12MD007595‐05 from the National Institute on Minority Health and Health Disparities, and an Institutional Development Award (IDeA) from the National Institut