Jenny Xiang's Lab at NCSU

Introduction

Our research applies multidisciplinary approaches to understand origin and evolution of biodiversity at morphology, genetics/genomics, and function levels with focuses on flowering plants. Our special interests are the order Cornales (dogwoods and relatives) and plant lineages discontinuously distributed in the north temperate forests of eastern Asia and eastern North America. By integrating phylogenetics, evolutionary developmental genetics, and bioengineering, we aim to understand the genetic basis regulating the evolution of floral display strategies in the dogwood family, and generate new varieties that may be heat or disease resistant for horticulture uses. By integrating phylogeny, biogeography, population genetics, and climatic modeling, we construct the evolutionary histories of plants in space and time, predict effects of climatic changes on species' range shifts, evaluate genetic health of rare and/or endangered species, and further we attempt to uncover patterns and rates of species differentiation/speciation and the underlying causes. Using gene genealogy as a basis, we test systematic and evolutionary hypotheses (e.g., organismal trait evolution, hybridization, and polyploidy, etc.), using data obtained from DNA sequencing, gene expression, morphology of modern taxa and fossils.

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Biodiversity, Phylogeography, & Conservation Genetics

The Xiang's lab recently focuses on studying the biodiversity, phylogenetics, and evolution of genera discontinuously distributed in the north temperate deciduous forests of eastern Asia and North America. The project is a part of an national and international collaborative larger project led by University of Florida (US leading institute) that is supported by an US-China Dimension of Biodiversity grant of National Science Foundation. The forests of eastern Asia and eastern North America were anciently connected and have a shared evolutionary and ecological history; they offer an excellent opportunity to study the drivers of biodiversity across geographic space and through evolutionary time. The research uses an integrative approach and genome-wide molecular markers to model the biogeographic history and evolution of Aesculus (buckeyes and horse chestnuts), Nyssa (black gum, tupelo), Castanea (chestnuts), Cornus (dogwoods), Torreya (nutmegs) and identify the ecological drivers underlying the spatial patterns of diversity within and between continents. Information from historical connections, current patterns, and future species distribution models are integrated to better understand and conserve the biodiversity in our planet's ecosystems.

Dr. Xiang and colleagues at University of Georgia has been working together during the past a few years on a phylogenomic study of the dogwood order Cornales and on sequencing the genome of the state flower Cornus florida. To aid conservation of the species that has been threathened by fungal diseases, Xiang's lab has worked on characterizing the genetic diversity and ecological niches of the species, and identifying genetic markers associated with fungal diseases and environmental variables in natural populations. Using the landscape genetics/genomics and genotyping by sequencing approaches, they elucidated how genetic variation in natural populations of the species responds to landscape and environments heterogeneity and identified loci selected for local adaptation. The work was in collaboration with Dr. Ross Whetten in Forestry Department. In collaboration with Dr. Sirius Li in PMB, they also investigated variation of foliar secondary metabolomes in the species to determine how genetic diversity and diseases affect chemical diversity and identified metabolites associated with adaptive loci responsible for plant immunity to diseases.

Evolutionary Development & Functional Genetics/Genomics of Dogwoods (Cornus L.)

Inflorescence is important to angiosperm reproduction. Alterations in inflorescence architecture may result in evolutionary innovations driving new ecological adaptation and speciation. Despite the importance of understanding the genetic basis of inflorescence evolution, little progress has been made. The dogwood genus, containing our state flower, display remarkable variation in the morphology of inflorescences, making it a rare but excellent system for evolutionary developmental study of inflorescences. Xiang's lab had been investigating the genetic mechanisms driving the evolution of inflorescence variation in dogwoods in collaboration with Dr. Xie and Dr. Franks. A combination of techniques in molecular biology, developmental genetics, and phylogenetics, including quantitative PCR, in-situ hybridization, transcriptome sequencing, and genetic transformation, were applied to the study. They successfully established an agrobacterium mediated genetic transformation system in the bunchberry (Cornus canadensis) and used the system to validate functions of candidate key inflorescence regulators. Through comparative analyses of spatiotemporal expression patterns of these genes among species based on a phylogeny, they identified evolutionary changes in gene expression that were correlated with morphological modifications in inflorescence structure, and proposed a molecular model explaining the evolutionary alteration of inflorescence in the dogwood genus. A set of putative candidate genes were identified through comparative transcriptome sequencing.