Maternal Embryo Effect Arrest 31 (MEE31) is a moonlighting protein involved in GDP-D-mannose biosynthesis and KAT1 potassium channel regulation

[EN] Due to anthropogenic global warming, droughts are expected to increase and water availability to decrease in the coming decades. For this reason, research is increasingly focused on developing plant varieties and crop cultivars with reduced water consumption. Transpiration occurs through stomatal pores, resulting in water loss. Potassium plays a significant role in stomatal regulation. KAT1 is an inward-rectifying potassium channel that contributes to stomatal opening. Using a yeast high-throughput screening of an Arabidopsis cDNA library, MEE31 was found to physically interact with KAT1. MEE31 was initially identified in a screen for mutants with delayed embryonic development. The gene encodes a conserved phosphomannose isomerase (PMI). We report here that MEE31 interacts with and increases KAT1 activity in yeast and this interaction was also confirmed in plants. In addition, MEE31 complements the function of the yeast homologue, whereas the truncated version recovered in the screening does not, thus uncoupling the enzymatic activity from KAT1 regulation. We show that MEE31 over expression leads to increased stomatal opening in Arabidopsis transgenic lines. Our data suggest that MEE31 is a moonlighting protein involved in both GDP-D-mannose biosynthesis and KAT1 regulation.This work was supported by grant PID2019-104054GB-I00 financed by the Ministerio de Ciencia e Innovacion, Spain (MCIN/AEI/10.13039/501100011033).González-García, A.; Kanli, M.; Wisowski, N.; Montoliu-Silvestre, E.; Locascio, AAM.; Sifres Cuerda, AG.; Gómez, M.... (2024). Maternal Embryo Effect Arrest 31 (MEE31) is a moonlighting protein involved in GDP-D-mannose biosynthesis and KAT1 potassium channel regulation. Plant Science. 338. https://doi.org/10.1016/j.plantsci.2023.11189733

Genome Wide Binding Site Analysis Reveals Transcriptional Coactivation of Cytokinin-Responsive Genes by DELLA Proteins

[EN] The ability of plants to provide a plastic response to environmental cues relies on the connectivity between signaling pathways. DELLA proteins act as hubs that relay environmental information to the multiple transcriptional circuits that control growth and development through physical interaction with transcription factors from different families. We have analyzed the presence of one DELLA protein at the Arabidopsis genome by chromatin immunoprecipitation coupled to large-scale sequencing and we find that it binds at the promoters of multiple genes. Enrichment analysis shows a strong preference for cis elements recognized by specific transcription factor families. In particular, we demonstrate that DELLA proteins are recruited by type-B ARABIDOPSIS RESPONSE REGULATORS (ARR) to the promoters of cytokinin-regulated genes, where they act as transcriptional co-activators. The biological relevance of this mechanism is underpinned by the necessity of simultaneous presence of DELLAs and ARRs to restrict root meristem growth and to promote photomorphogenesis.This work was funded by grants BIO2007-60923 and BIO2010-15071 from the Spanish Ministry of Economy and Innovation (MAB); grant ERC-2011-StG_20101109 from the European Research Council (JUL); grants BB/J/00426X/1 and BB/E022618/1 from the Biotechnology and Biological Sciences Research Council (SGT); the Professorial Research Fellowship award BB/G023972/1 from the Biotechnology and Biological Sciences Research Council (KH and MJB); and grant FP7-311929 from the European Union (RPB). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Marín-De La Rosa, NA.; Pfeiffer, A.; Hill, K.; Locascio ., AAM.; Bhalerao, R.; Miskolczi, P.; Grønlund, A.... (2015). Genome Wide Binding Site Analysis Reveals Transcriptional Coactivation of Cytokinin-Responsive Genes by DELLA Proteins. PLoS Genetics. 11(7):1-20. https://doi.org/10.1371/journal.pgen.100533712011

BCL2-ASSOCIATED ATHANOGENE4 Regulates the KAT1 Potassium Channel and Controls Stomatal Movement

[EN] Potassium (K+) is a key monovalent cation necessary for multiple aspects of cell growth and survival. In plants, this cation also plays a key role in the control of stomatal movement. KAT1 and its homolog KAT2 are the main inward rectifying channels present in guard cells, mediating K+ influx into these cells, resulting in stomatal opening. To gain further insight into the regulation of these channels, we performed a split-ubiquitin protein-protein interaction screen searching for KAT1 interactors in Arabidopsis (Arabidopsis thaliana). We characterized one of these candidates, BCL2-ASSOCIATED ATHANOGENE4 (BAG4), in detail using biochemical and genetic approaches to confirm this interaction and its effect on KAT1 activity. We show that BAG4 improves KAT1-mediated K+ transport in two heterologous systems and provide evidence that in plants, BAG4 interacts with KAT1 and favors the arrival of KAT1 at the plasma membrane. Importantly, lines lacking or overexpressing the BAG4 gene show altered KAT1 plasma membrane accumulation and alterations in stomatal movement. Our data allowed us to identify a KAT1 regulator and define a potential target for the plant BAG family. The identification of physiologically relevant regulators of K+ channels will aid in the design of approaches that may impact drought tolerance and pathogen susceptibility.The authors would like to thank Elena Moreno, María José Falaguer, Alejandro Mossi, Sara Aljama, José Antonio Navarro, Vicente Pallás, Daniel Franco-Aragón, Jorge Lozano, and Stan Gelvin for assistance in the completion of this work and for providing reagents. This work was supported by the Spanish Ministry of Economy and Competitiveness (BIO201677776-P and BIO2016-81957-REDT) and the Valencian Government (AICO/2018/300).Locascio, AAM.; Marques Romero, MC.; García-Martínez, G.; Corratgé-Faillie, C.; Andrés-Colás, N.; Rubio, L.; Fernández, JA.... (2019). BCL2-ASSOCIATED ATHANOGENE4 Regulates the KAT1 Potassium Channel and Controls Stomatal Movement. PLANT PHYSIOLOGY. 181(3):1277-1294. https://doi.org/10.1104/pp.19.00224S12771294181