The Evolution and Development of Compound Leaves

University Of California-Davis, Davis CA

Investigators

Abstract

Leaves function in photosynthetic light capture and are critical both to individual plant survival and to energy exchanges on a global scale. Based on their morphology leaves can be broadly grouped into two categories, simple and compound. Each of these leaves may have advantages over the other depending on the environment in which they evolved. However, the developmental basis for the various leaf forms seen in nature is largely unexplored. Dr. Sinha has undertaken a systematic dissection of compound leaf shape in the model organism tomato using genetic, molecular and developmental tools. When compared to results from simple leafed model species, these results suggest to us the commonalities and divergences between the compound and simple modes of leaf development. Her previous results suggested that the Class 1 KNOTTED-like HOMEOBOX (KNOX1) genes function differently in tomato (with compound leaves) and Arabidopsis (with simple leaves) and subsequent data showed that KNOX1 genes are utilized in the developmental cascade leading to compound leaves in most flowering plants. Dr. Sinha has extended this study to analyze the role of PHANTASTICA, a MYB domain protein that regulates KNOX1 genes. In tomato leaf development PHAN and KNOX1 share a dosage sensitive regulatory relationship and PHAN regulates leaflet placement in numerous compound leaves. While these known genes are important determinants for leaf complexity, this work will also identify roles that other heretofore unexplored genes play in compound leaf development. This research involves analysis of leaf development in the tomato and bean families, and in related species in the same genus (e.g. the genus Lepidium) or within the same species (e.g. the heteroblastic species Neobeckia aquatica) in the mustard family. This research encompasses the areas of developmental biology, molecular biology, plant physiology, genetics, and evolutionary biology and the long-term goals are to thoroughly dissect compound leaf development in an evolutionary context.