Award Category

Natural Sciences and Mathematics

Publication Date



The lazy-2 mutation (lz-2) in tomato plants (Solanum lycopersicum) is exhibited as a phenotype of light-dependent reversed-gravitropism. The mutation’s centromeric location has only allowed for speculation on the identity of the lz-2 gene. In order to investigate the relationship and affect of thelz-2 mutation on signaling pathways linked to auxin growth hormone regulation, global gene activity was assessed. Modern molecular biology tools including microarray technology and various PCR techniques were utilized to generate a list of significantly differentially regulated genes in lz-2 mutant plants compared to wild-type plants. Gene ontology functional analysis indicated that genes involved in protein ubiquitination constituted the largest percentage of differentially expressed genes, while signal transduction genes were also a significant fraction of all genes studied. Top gene candidates were tested by qPCR to verify statistically significant up- or down-regulation in lz-2 mutant plants. Two such candidates, a gene encoding an f-box family protein and the ATCUL1 gene encoding a cullin protein have been implicated as major components of the SCF ubiquitin-ligase complex, which degrades auxin repressor proteins. This study suggests a potential relationship between differential expression of ubiquitin-ligase proteins causing altered auxin signaling and the downward growth of lz-2 mutant tomato plants in response to gravity.

Faculty Advisor

Andreas Madlung


Biology 404: Molecular Biology