Escalante (2021): A Dictyostelium model for BPAN disease reveals a functional relationship between the WDR45/WIPI4 homolog Wdr45l and Vmp1 in the regulation of autophagy-associated PtdIns3P and ER stress, Autophagy,

SummarySymbiotic nitrogen fixation carried out by the interaction between legumes and rhizobia is the main source of nitrogen in natural ecosystems and in sustainable agriculture. For the symbiosis to be viable, nutrient exchange between the partners is essential. Transition metals are among the nutrients delivered to the nitrogen‐fixing bacteria within the legume root nodule cells. These elements are used as cofactors for many of the enzymes controlling nodule development and function, including nitrogenase, the only known enzyme able to convert N2 into NH3. In this review, we discuss the current knowledge on how iron, zinc, copper, and molybdenum reach the nodules, how they are delivered to nodule cells, and how they are transferred to nitrogen‐fixing bacteria within.

Cu+-chaperones are a diverse group of proteins that allocate Cu+to specific copper-proteins, creating different copper pools targeted to specific physiological processes. Symbiotic nitrogen fixation carried out in legume root nodules requires relatively large amounts of copper, for which targeted copper deliver systems would be required. MtNCC1 is a nodule-specific Cu+-chaperone encoded in theMedicago truncatulagenome, with a N-terminus Atx1-like domain that can bind Cu+with picomolar affinities. This gene is expressed primarily from the late infection zone to the early fixation zone, and is located in the cytosol, associated to plasma and symbiosome membranes, and within nuclei. Consistent with its key role in nitrogen fixation,ncc1mutants have a severe reduction of nitrogenase activity, and a 50% reduction in copper-dependent cytochromecoxidase activity. A subset of the copper-proteome is also affected in the mutant nodules. Many of these proteins can be pulled-down when using a Cu+-loaded N-terminal MtNCC1 moiety as a bait, indicating a role in nodule copper homeostasis and in copper-dependent physiological processes. Overall, these data suggest a pleiotropic role of MtNCC1 in copper delivery for symbiotic nitrogen fixation.