Divergent Cell Wall Remodelling in Maize Under Cold or Drought

Abstract

The plant cell wall is the first line of defense against environmental changes. We previously described that the maize B73 is a stalk-lodging resistant inbred that undergoes extensive modifications in general physiology and cell wall composition under drought. To extend these findings, we investigated cell wall responses under cold, which represents another major abiotic stress. We found that cold stress does not alter total lignin or cellulose contents but induces qualitative changes in cell wall architecture, including shifts in lignin composition and modifications in hemicellulose and pectin organization. Transcriptomic analyses revealed that cell wall genes are predominantly induced by cold stress, contrasting with the general repression previously observed under drought. Integration of cold and drought transcriptomic datasets revealed six co-expression patterns for cell wall genes, including genes with specific and shared patterns of response to both stresses. We classified the cell wall genes from each pattern according to their biological roles, and our results suggest that cold-triggered inductions enhance cell wall remodeling, while drought-triggered repressions promote energy conservation and growth-limiting strategies. Transcription factor enrichment identified potential regulators of cell wall genes upon one or both stresses. By integrating these predicted transcriptional regulatory networks with the cell wall genes expression alteration patterns, we propose that the cold-induced remodeling of the cell wall is driven by broad regulatory networks, whereas drought-induced resource conservation is controlled by a small number of central regulators.