Environmental arsenic contamination adversely affects human health, and its accumulation diminishes food quality. Glutathione (GSH) is known to bind and detoxify arsenic and other toxic metals. GSH homeostasis in living cells is maintained via γ-glutamyl cycle. Previously, γ-glutamyl cyclotransferases ( GGCTs) have been shown to be involved in GSH degradation in plants and increasing tolerance to toxic metals. Here we characterized the GGCT2;1 homolog from Camelina sativa for its role in arsenic tolerance and accumulation. Overexpressing CsGGCT2;1 in Camelina resulted in strong tolerance to arsenite (AsIII). Compared to wild-type, overexpression (OE) lines had significantly higher shoot (2.6-3.5-fold) and root (7-10-fold) biomass on AsIII containing media and accumulated 40-60% less arsenic in root and shoot tissues. Further, OE lines had higher chlorophyll content, lower lipid peroxidation and oxidative stress. There was a small but nonsignificant increase in 5-oxoproline (5-OP) in OE lines and the upregulation of Oxoprolinase 1 ( OXP1) suggested accelerated conversion of 5-OP to glutamate, which is then utilized for GSH resynthesis for maintaining homeostasis. Overall, overexpression of GGCT2;1 and it homologs in Camelina and other crops will enable their cultivation on contaminated marginal lands to reduce As accumulation, addressing food safety issues as well as future food and biofuel needs.

Homology-directed repair of a defective glabrous gene in Arabidopsis with Cas9-based gene targeting  [Florian Hahn, Marion Eisenhut, Otho Mantegazza, Andreas P.M. Weber, January 5, 2018, BioRxiv] [https://doi.org/10.1101/243675]Overview and take-home messages:    Hahn et al. have compared the efficiencies of two different methods that have been previously reported to enhance the frequency of homologous recombination in plants. The paper has focused on testing a viral replicon system with two different enzymes, nuclease and nickase, as well as an in planta gene targeting (IPGT) system in  Arabidopsis thaliana. Interestingly, authors have chosen GLABROUS1 (GL1), a regulator of trichome formation, as a visual marker to detect Cas9 activity and therefore homologous recombination. A 10 bp deletion in the coding region of GL1 gene produces plants devoid of trichomes. Out of the two methods in planta gene targeting approach successfully restored trichome formation in less than 0.2% of ~2,500 plants screened, whereas the method based on viral replicon machinery did not manage to restore trichome formation at all. This manuscript is of high quality, experiments are well designed and executed. However, there are some concerns that could be addressed in the next preprint or print version. Below are some feedback and suggestions that we hope will improve the manuscript.

Medicago truncatula Zinc-Iron Permease6 provides zinc to rhizobia-infected nodule cells [Isidro Abreu, Angela Saez, Rosario Castro-Rodriguez, Viviana Escudero, Benjamin Rodriguez-Haas,  Marta Senovilla, Camille Laure, Daniel Grolimund, Manuel Tejada-Jimenez, Juan Imperial, Manuel Gonzalez-Guerrero , January 24, 2017 (preprint),  September 21, 2017 (in print), BioRxiv & Wiley-Blackwell]