Malcomber Lab Research


	Research
		The grass family (Poaceae), the 5^th largest plant family, comprises approximately 10,000 species and includes the cereal crops barley, corn, oats, rice, rye, sorghum, tef and wheat. These grass species provide the bulk of human caloric intake and the grass family dominates ecologically important habitats throughout the world. During the domestication of cereal crops, humans selected for plants with particular characters to improve yield. Because flower number directly impacts grain number, floral characters were a focus of this intense selection. Botanists differentiate members of the grass family on the basis of the size and shape of floral organs, how many flowers are collected into specialized structures called spikelets, how these spikelets are arranged on branches, and how many branches are on an inflorescence. A fundamental question in evolutionary biology is what genes cause species to look different. This question is now tractable for major groups of grass species. Sophisticated programs for modeling the evolutionary process, coupled with faster computers, have led to better-supported estimates of relationships within graminoid Poales (Figure 1). New technologies for gene sequencing, cloning and expression have led to a large and growing list of genes from rice and corn that regulate inflorescence development (Figure 2). Synthesizing these data, we have an extensive list of genes that likely contributed to the diversity of grass inflorescence morphology and an evolutionary framework of where patterns of gene expression or function are expected to have changed (Malcomber et al., 2006). We are investigating the evolution of a series of genes that regulate diverse aspects of inflorescence and flower development in grasses and immediate grass relatives (graminoid Poales). By integrating diverse phylogenetic, developmental morphological, molecular and developmental genetic approaches we aim to test whether the same genes that regulate morphological development in model species such as rice and maize are the same that have affected morphological diversification within graminoid Poales. We collaborate with several people including Andrew Doust (Oklahoma State University, Stillwater), Dave Jackson (Cold Spring Harbor Laboratories), Toby Kellogg (University of Missouri - St. Louis), Paula McSteen (Penn State University) and Bob Schmidt (University of California, San Diego). Please contact me (smalcomb@csulb.edu) if you are interested in pursuing a Master's degree in my lab.

	Figure 1. Relationships among grasses and immediate relatives based on phylogenetic analyses of multiple genetic loci. Thick branches are supported by > 95% bootstrap. Based on Grass Phylogeny Working Group (2001), Bremer (2002) and Michelangeli et al. (2003). Immediate grass relatives have a typical monocot flower with two alternating whorls of three tepals. The earliest diverging grasses, Streptochaeta and Anomochloa, have flowers in 'spikelet equivalents' whereas all other grasses have their flowers arranged in spikelets.

		Figure 2. Inflorescence development in Arabidopsis and corn (Zea mays) starting with vegetative meristem and ending with floral meristems, and the genes that are known to affect particular stages. Boldface, cloned genes. Gene names in red are actively being investigated in the Malcomber lab (see People for list of researchers studying the different genes) BA1, BARREN STALK1; BIF2, BARREN INFLORESCENCE2; FUL = FRUITFUL, KNOX, KNOTTED1-like HOMEOBOX; LAX, LAX PANICLE1, RA3, RAMOSA3; RCN, RICE CENTRORADIALIS; SEP, SEPALLATA. (Figure modified from Malcomber et al. 2006)
	last modified March 2007