4 O'Clock Forum: Unveiling genetic redundancy mechanisms in developmental regulatory circuits by genome edition in maize

Thursday, November 21, 2019 16:00
Raymond Building R3-048, 21111 Lakeshore Road, St Anne de Bellevue, QC, H9X 3V9, CA

4 O'Clock Forum continues this year's seminar series with a talk by Dr. Edgar Demesa-Arevalo, Post Doctoral Fellow, Cold Spring Harbor

Food security represent a big challenge nowadays, due to the dramatic increase of population and climate change the land extensions destined to produce crops has been reduced and increasing crops yields is one alternative to solve this problem. Maize is one of the most important crops worldwide and has been used not only as an agronomic model but also as a genomic, physiological, genetic and developmental model. To increase seed production in corn, we need to understand the molecular basis behind this process. The seeds are nurtured in the female inflorescence, once the female flowers are pollinated. Inflorescence development is tightly regulated, and variation in cob shapes can be explained by alterations in regulatory circuits of meristem maintenance. The core mechanism is highly conserved across species. However, the particularities of each plant have evolved variations to guarantee the proper function of  inflorescence meristems. CLE peptides are the signaling molecules perceived in the stem cell niche to establish a balance between proliferation and differentiation. In Arabidopsis, CLAVATA3 (CLV3) is the main peptide involved in this process, while its ortholog in maize was not clear. Using a novel multi-guide RNA (gRNA) CRISPR/Cas9 approach we generate mutations in two closer orthologs to CLV3 in maize and other eight maize CLE peptides (ZmCLEs) expressed in meristems. By molecular functional characterization, we found ZmCLE7 is the ortholog to CLV3, and the lack of this is partially compensated by a second CLE peptide: ZmFCP1. ZmCLE7 mutants showed meristem fasciation or over proliferation, a trait that, potentially, can be fine-tuned to increase the space to bear seeds. We are currently characterizing additional ZmCLE mutants, trying to identify if these compensation mechanisms are regulating other meristematic entities in corn. Additionally, we are targeting other gene families that might be involve in suppressing meristem determinacy; we can generate quadruple mutants using our multi-guide arrays. The  study of meristem regulation has allowed us to discover and shape new agronomical traits that can contribute to increase crop yield in cereals.


Dr. Edgar Demesa-Arevalo started his scientific training doing his BSc thesis in the Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN) in Mexico City, trying to understand the establishment of symbiotic mycorrhizas. He did his Ph.D. in CINVESTAV campus Irapuato (México) under the mentorship of Jean-Philippe Vielle-Calzada, identifying the nature of the signals involved in the vegetative to reproductive phase in Arabidopsis. Later, he joined Dave Jackson’s Lab in Cold Spring Harbor Laboratory (USA), focusing his research on two main topics, the establishment of transgenic lines as a resource for maize community and investigating the molecular mechanisms involved in meristem regulation in maize. He also optimized a multiple-sgRNA array for CRISPR/Cas9 in maize, widely used in maize community nowadays.

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