Elevated temperatures can adversely affect pollen development by influencing the function of a nurturing cell layer called the tapetum cell layer in the stamens of angiosperm flowers, causing pollen abortion and male sterility. Recent studies in A. thaliana have shown that clusters of physically linked genes on the chromosomes co-express in the tapetum cell layer at the time when the flowers are the most sensitive to heat stress. To study the evolutionary forces that drive cluster formation, I will study these clusters in Brassica oleracea. I will also address the hypothesis that the gene clusters participate in the plants response to heat stress. To this end, I will: i) acquire transcriptome data from tapetum cells using Laser Capture Microdissection followed by massively parallel sequencing of mRNAs, ii) perform a comparative cluster analysis in B. oleracea and A. thaliana using a combination of computational, experimental studies of gene functions;