Sydney, Australia

Postdoctoral fellow

BSc (Hon) - The University of Sydney, Australia

PhD - The University of Melbourne, Australia

Introduction

My primary interest is in studying the evolution of morphological diversity from a phylogenetic and developmental perspective. My goal is to integrate phylogenetic hypotheses with underlying mechanisms of gene action to explain how morphological diversity arises. I am particularly interested in the evolution of developmental pathways, primarily from a developmental morphology point of view, but stretching into shifts in timing and location of patterns of gene expression. I have also had success in identifying candidate genes for developmental and morphological evolution through QTL analyses of species crosses where the two parents differ significantly in important morphological characters. I see a developmental focus as key in integrating morphological and genetic studies. Understanding the evolution of development in the framework of molecular phylogenies allows us to link the developmental trajectories of a population of individuals with those changes in trajectory that lead to morphologically distinguishable species. This approach attempts to bridge the gap between micro-evolutionary processes and macro-evolutionary patterns.

Inflorescence diversity in the millet grasses (Paniceae, Poaceae)

I am presently working on a number of inter-related projects linking evolution and development in grasses. The first project concerns inflorescence diversity in the 'bristle clade' millet grasses. This group includes the three large genera Setaria, Pennisetum and Cenchrus, and contains foxtail millet (S. italica) and pearl millet (P. glaucum). All members of the group have bristles (sterile branchlets) as well as spikelets in the inflorescence, but inflorescences range from condensed heads with many orders of branching to elongate racemose panicles with few orders of branching. The inflorescence diversity in these three genera has been studied in a phylogenetic context, using the chloroplast markers ndhF and trnL, and has confirmed the close relationship between Pennisetum and Cenchrus, but has surprisingly suggested that both Pennisetum and Setaria are paraphyletic. The developmental analyses have shown that only a few developmental changes are need to create the diversity of inflorescences seen at maturity. Work is also underway in the lab by undergraduates Anya Penley and Shelby Kleweis, who are sequencing the nuclear markers phytochrome B and a variable intron of knotted1 respectively. These will be used to further elucidate the relationships of the subclades within the 'bristle clade', as well as to test for suspected patterns of hybridization within the group. Two papers from this work have recently been published.

A related project in the lab is a survey of inflorescence development and morphology in the panicoid grasses, a large group of some 3000 species that contains maize, sorghum and sugarcane. The survey, undertaken together with recent master's graduate Ken Hiser, master's candidate Emilie Bess and Professor Elizabeth Kellogg, is a continuation of work started by Professor Kellogg and Lucia LeRoux. A comparison of groups based on inflorescence types with groups obtained from analysis of molecular marker sequences shows that similar inflorescence forms have evolved repeatedly in different groups. This may imply that only a few genes control the developmental inflorescence morphology.

Quantitative Trait Loci (QTL) studies in foxtail millet

To examine the hypothesis that changes in inflorescence morphology are due to the action of only a few genes of largeeffect, we are doing a QTL analysis of a cross between foxtail millet (S. italica) and green millet (S. viridis), the wild species from which S. italica was domesticated. The seed for this cross was donated by our collaborators Drs. Katrien Devos and Mike Gale, of the John Innes Center, Norwich, U.K. The two parents have very different inflorescences, and the 120 segregating F2 populations show different combinations of inflorescence morphology traits. By relating the distribution of morphological traits across the F2 populations to a genomic map prepared from RFLP markers by our collaborators at the John Innes Center, we can establish areas on the chromosomes that control the expression of these traits. This work has shown that only a few major gene clusters control most of the variation in inflorescence form. Comparative mapping of QTL from the foxtail millet genome to the maize and rice genomes has allowed likely candidate genes to be identified. In several cases, map hybridization of probes of those candidate genes has shown that they are in the genome regions predicted through comparative mapping. Some QTL regions, however, do not have any likely candidate genes (as identified through similar mutant phenotypes), and these are the focus of our present investigations.

Floral development and variation in Winteraceae:

My interests arising from my PhD research on floral development and floral variation in the basal angiosperm family Winteraceae are both evolutionary and structural. In particular, the method by which different floral morphologies in the family arise through modifications of the developmental process remains an important focus, especially in the Australian genus Tasmannia, where two sharply different developmental programs can be found. The study of floral variation in Drimys winteri has revealed that apical meristem size and shape have a major influence on eventual floral form. Variation in these physical parameters is dependent on the position of the flower in the inflorescence, resulting in flowers on a single tree that vary greatly in organ number and arrangement. Two papers from this work have recently been published.

Selected Publications (some citations are linked to a downloadable pdf):

Doust, A.N. and E.A. Kellogg (accepted). The effect of plant density on branching in weedy and domesticated millet grasses. Molecular Ecology.

Devos, K.M., J. Beales, Y. Ogihara and A.N. Doust. 2005. Comparative sequence analysis of the Phytochrome C gene and its upstream region in allohexaploid wheat reveals new data on the evolution of its three constituent genomes. Plant Molecular Biology 58: 625-641.

Doust, A.N. and P.F. Stevens. (in press). A reinterpretation of the staminate flowers of Haptanthus. Systematic Botany

Doust, A.N., K.M. Devos, M. Gadberry, M.D. Gale, and E.A. Kellogg. 2005. The genetic basis for inflorescence variation between foxtail and green millet (Poaceae). Genetics 169: 1659-1672.

Bess, E.C., A.N. Doust, and E.A. Kellogg. 2005. A naked grass in the "bristle clade": a phylogenetic and developmental study of Panicum section bulbosa (Paniceae: Poaceae). International Journal of Plant Sciences 166: 371-381.

Gadberry, M.D., S.T. Malcomber, A.N. Doust, and E.A. Kellogg. 2004. Primaclade - A flexible software tool to find conserved PCR primers across multiple species. Bioinformatics 21:1263-1264.

Doust, A.N., K.M. Devos, M. Gadberry, M.D. Gale, and E.A. Kellogg. 2004. Genetic control of branching in the foxtail millet. Proceedings of the National Academy of Sciences 101: 9045-9050.

Kellogg, E.A., K. Hiser,and A.N. Doust. 2004. Taxonomy, phylogeny, and inflorescence development of the genus Ixophorus (Panicoideae, Poaceae). International Journal of Plant Sciences 165:1089-1105.

Doust, A.N. and A.N. Drinnan. 2004. Floral development and molecular phylogeny support the generic status of Tasmannia (Winteraceae). American Journal of Botany 91: 321-331.

Doust, A.N. and E.A. Kellogg. 2002. Inflorescence diversification in the panicoid "bristle grass" clade (Paniceae, Poaceae): evidence from molecular phylogenies and developmental morphology. American Journal of Botany 89: 1203-1222.

Doust, A.N. and E.A. Kellogg. 2002. Integrating phylogeny, developmental morphology and genetics: a case study of inflorescence evolution in the Ôbristle grassÕ clade (Panicoideae, Poaceae). In Cronk, Q. Bateman, R. and J. Hawkins (Eds), Developmental Genetics and Plant Evolution, Taylor & Francis, London.

Doust, A.N. 2001. The developmental basis of floral variation in Drimys winteri (Winteraceae). International Journal of Plant Sciences 162: 697-717.

Doust, A.N. 2000. Comparative floral ontogeny in Winteraceae. Annals of the Missouri Botanic Gardens 87: 366-379.

Conn, B.J. and A.N. Doust 1997. Revision of Xyris section Pomatoxyris (Xyridaceae) in Australia. Australian Systematic Botany 10: 189-248.

Doust, A.N. and B.J. Conn 1994. Xyris L. section Xyris (Xyridaceae) in Australia. Australian Systematic Botany 7: 455-484.

Doust, A.N. and B.J. Conn 1993. Xyris L. (Xyridaceae). In Harden, G. (Ed) Flora of New South Wales 4: 261-263. New South Wales University Press.

Doust, A.N. and J. Everett 1992. Pycnosorus Benth. (Asteraceae: Gnaphalieae). In Harden, G. (Ed) Flora of New South Wales 3: 260-262. New South Wales University Press.

Everett, J. and A.N. Doust 1992. New species in Craspedia sens. strict. (Asteraceae: Gnaphalieae). Telopea 5: 35-38.

Everett, J. and A.N. Doust 1992. New species and a new combination in Pycnosorus (Asteraceae: Gnaphalieae). Telopea 5: 39-44.

Everett, J. and A.N. Doust 1992. In Harden, G. (Ed) Craspedia Forst. f. (Asteraceae: Gnaphalieae). Flora of New South Wales 3: 221-226. New South Wales University Press.