Speakers

Biography

Silvia Calderone, a 4^th-year PhD candidate at the Centre for Research in Agricultural Genomics (CRAG) in Barcelona, Spain, explores the intricacies of metabolic engineering of lignocellulosic biomass and the molecular mechanisms of circadian clock function in maize, under the guidance of PhD David Caparrós and PhD Paloma Mas. Her academic journey includes an M.Sc. in Plant Biotechnology – Molecular Plant Breeding and Pathology from Wageningen University and Research. Silvia's keen interests revolve around unraveling the molecular secrets of plant development and their adaptive responses to environmental stresses, showcasing her passion for advancing agricultural genomics.

Abstract

In maize (Zea mays L.), a globally cultivated and strategic crop, stalk-lodging and drought are two significant stressors affecting yield. However, little is known about the impact of drought on maize varieties and their stalk-lodging resistance. The plant cell wall is a dynamic and adaptable structure, crucial as the first defense against environmental challenges. Maize, as all commelinid monocot species, is characterised by a type II cell wall, where the main hemicellulose is arabinoxylan instead of xyloglucan, typically present in type I cell walls.

In this study, we explored the cell wall biochemical and molecular mechanisms underlying the responses to drought of two maize inbreds with opposite stalk-lodging phenotypes, one resistant and one susceptible to this stress. We characterized the different cell wall biochemical alterations and associated those changes with differential gene expression patterns during drought stress, especially in cell wall-related genes. Identifying sets of genes differentially expressed in the two inbreds prompted us to search for transcription factors that might be acting as upstream regulators.

Our results revealed unique adaptive strategies in response to drought in each inbred, offering valuable insights into the broader context of plant adaptation. Surprisingly, the stalk-lodging-resistant inbred was more severely affected by drought than the lodging-susceptible inbred. The latter responded by increasing arabinose-enriched polymers, pectins, and their side-chain modifications while decreasing lignin content. In contrast, the stalk-lodging resistant inbred displayed a more profound rearrangement of cell walls, including alterations in lignin composition and increased uronic acids conjugated with hemicelluloses. Transcription factor enrichment assays uncovered some inbred-specific gene regulatory networks that may orchestrate the expression of cell wall genes specific to each inbred, possibly in an ABA-dependent manner.

These findings reveal that the stalk-lodging susceptible inbred had a more dynamic, loose, and plastic cell wall matrix. In contrast, the stalk-lodging resistant inbred required a more profound reprogramming of cell wall genes to readapt its cell wall metabolism to drought conditions. Therefore, the high selection pressure upon breeding to increase stalk-lodging resistance had possibly led to a reduced cell wall plasticity, affecting its capacity to face drought stress.

Our work underscores the critical role of the cell wall polymers and their side-chain modifications during drought stress, controlling the hydration of the cell wall and serving as a determinant factor in protecting plants from this stress. In conclusion, this study contributes to unraveling the complexity of maize responses to various environmental stressors, emphasizing the need to consider inbred-specific biochemical and molecular mechanisms to enhance crop resilience and agricultural sustainability.