The marginal meristem and the evolution and development of fern leaves

• Grant number: 24/20792-3
• Support Opportunities: Research Grants - Young Investigators Grants
• Start date: October 01, 2025
• End date: September 30, 2030
• Field of knowledge: Biological Sciences - Botany - Plant Morphology
• Principal Investigator: Rafael da Silva Cruz
• Grantee: Rafael da Silva Cruz
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated researchers: Alejandra Vasco ; Alexander Hetherington ; Barbara A. Ambrose ; Gladys Flávia de Albuquerque Melo de Pinna ; Jefferson Prado

Abstract

This project will explore the evolution and development (evo-devo) of apical and marginal meristems in fern leaves through a detailed study of structural features, gene evolution, and gene expression. The motivation behind it is to understand the origin and formation of leaves (megaphylls) in ferns - an under-explored group in terms of its ontogenetic aspects. Ferns occupy a key phylogenetic position for understanding the evolution and development of vascular plant leaves. Although leaves are the major photosynthetic organs of plants, their origin and development are still not fully understood.The telome theory, the most widely accepted explanation for leaf origin, lacks evidence for one of its main processes, webbing, which is necessary for development of the leaf lamina. The lateral growth, more specifically the latero-apical expansion of the leaf apical meristem, could explain the leaf development of many species of ferns.Leading a team of experts, I will study the structure of marginal meristems across diverse fern clades to determine their role in the evolution of the leaf blade formation. We will also conduct molecular anatomy analyses of expression of the genes Class I KNOX (involved in meristem maintenance) and CUC (involved in specifying boundary of organs, as demonstrated only for angiosperms so far) in the model fern Ceratopteris richardii Brongn. to explore these mechanisms in fern development.The methodology encompasses classic anatomical studies with molecular analyses. The project's timeline, objectives, and expected contributions are outlined. The project aims to publish high-impact articles that challenge current paradigms and proposes a new model for fern leaf growth, ultimately establishing a research group in Brazil dedicated to the evolution and development of land plants. (AU)