Characterizing Stem Node Anatomy and Secondary Cell Wall Thickening in the Model Cereal Grass Brachypodium distachyon

Presenter: Kathryn McGillivray

Faculty Sponsor: Samuel P. Hazen

School: UMass Amherst

Research Area: Biology

Session: Poster Session 5, 3:15 PM - 4:00 PM, 163, C14

ABSTRACT

Nodes are critical yet understudied junctions in grass stems, serving as sites of leaf attachment, branching, and vascular integration. In the model cereal grass Brachypodium distachyon, internode anatomy and secondary cell wall properties have been well characterized, but comparable analysis of nodes remains limited. To address this gap, we used histological techniques to define distinct regions within mature stem nodes and to compare their secondary cell wall features with those of internodes. Our analysis reveals intense lignification and highly thickened cells within node tissue, likely to support the structural stability of the node as a junction for growth and vasculature. We also observed enlarged vascular bundles in the node compared to the internode, suggesting distinct functional organization related to water and nutrient transport across tissues. To investigate genetic regulation of these patterns, we examined the role of KNOTTED OF BRACHYPODIUM 7 (KNOB7), a putative negative regulator of secondary cell wall thickening previously characterized only in internodes. Quantification of cell wall thickness in internode and node tissues of knob7-1 and knob7-3 mutants revealed significant differences compared to wild-type plants in both regions. The differences in thickness in the node are similar to the internode, indicating similar regulation of cell wall synthesis despite their distinct differences in architecture and cell wall thickening patterns. By elucidating node structure and cell wall thickening patterns, our study aims to advance our understanding of plant development and transcriptional regulation.

RELATED ABSTRACTS