Seminarios IHSM La Mayora - Ignacio Ezquer (Università degli Studi di Milano)

Title: New insights into the role of cell wall modifications induced by α-XYLOSIDASE1: The impact in seed and fruit size Ignacio Ezquer Biosciences Department. University of Milano Abstract Cell wall modifications are of pivotal importance during plant development. Among cell wall components, xyloglucans are the most abundant hemicellulose in primary cell walls, and can connect the cellulose microfibril surface to affect cell wall mechanical properties. Changes in xyloglucan structure are known as the major factor regulating cell growth. Therefore, the degradation of xyloglucan is an important modification that alters the cell wall. The α -XYLOSIDASE1 (XYL1) gene encodes the only α-xylosidase acting on xyloglucans in Arabidopsis thaliana. Here, we show that mutation of α-xyl1 strongly influences seed size, seed germination, and fruit elongation. We found that the expression of XYL1 is directly regulated in developing seeds and fruit by the MADS-box transcription factor SEEDSTICK (STK). We demonstrate that XYL1 complements the stk smaller seed phenotype. Furthermore, using Atomic Force Microscopy (AFM) combined with cell wall composition analysis, we discuss the role of XYL1 activity in maintaining tissue stiffness and growth, confirming the importance of cell wall modulation in shaping organs. In addition, we will discuss other interesting aspects and multidisciplinary tools we are developing in the lab in order to understand the molecular mechanisms controlling the development of the seed. Biography Dr Ezquer obtained his degree in Agronomy, at Technical University of Valencia in 2005. Dr Ezquer started his scientific career in the lab of Ramon Serrano at the Institute for Plant Molecular and Cell Biology (IBMCP-CSIC) where he performed the thesis project in abiotic stress tolerance. In 2006 he joined the Agrotechnology and Food Innovations company (Wageningen, the Netherlands) where he worked as a research assistant in the “Postharvest quality” team. Dr. Ezquer completed his PhD thesis in 2011 under the supervision of Javier Pozueta at the Agrobiotechnology Institute (IdAB-CSIC) in Pamplona. There, he investigated the biochemical and molecular mechanisms leading to the over-accumulation of starch in plants interacting with microbes. He is also co-inventor of one “biotech” patent, related to the results of his PhD research on a method to increase starch accumulation and increased resistance to hydric stress in plants. After a short stay in Japan (Niigata University), in 2012 he joined Lucia Colombo’s lab (Milano University, Italy) as a postdoc granted by a Marie Curie fellowship where he developed a new research line on the molecular regulation of metabolism in the seed. In Milano, his main interests have been to identify and characterize the functions of key genes important for the seed and fruit formation and to generate knowledge for seed breeding. After a brief postdoctoral period at the Italian National Research council (CNR) in 2016 he joined the Biosciences department at Milano University as tenure track researcher. Currently, he is an Associate Professor for the Milano University (since 2022) where he teaches several courses for biological sciences. During the last years, his work has enabled to characterize the molecular, biophysical and metabolic pathways controlling the development of post-reproductive tissues in plants. He also studies the barriers of plant sexual reproduction and related signaling pathways. He is currently leading the “SEED TEAM” at the Biosciences department (Milano University) funded with international research projects (RISE-H2020, ERA-NET…). He is also member of the PhD school in Biotechnology, committee member of the Italian Botanical Society and guest editor in several journals.