<p> The plant hormone auxin plays a major role in shaping plant morphology and development, but the gene networks regulating its synthesis and transport are incompletely known. The maize <i>BARREN INFLORESCENCE 1</i> (<i>BIF1</i>) gene has recently been cloned and shown to play an important role in the early stages of polar auxin transport. Auxin is synthesized in shoot tips and transported basipetally through the plant shoot and acts as a morphogen by facilitating the degradation of transcriptional repressors in a concentration dependent manner. The <i>AUX/IAA</i> gene family encodes transcriptional repressors that regulate a subset of plant developmental responses governed by the transcription of early auxin inducible genes in plants. Although the maize <i>BIF1</i> gene is a member of the <i>AUX/IAA</i> gene family, the co-ortholog(s) of <i> BIF1</i> in <i>Arabidopsis thaliana</i> was not known prior to this research.</p><p> Bayesian phylogenetic reconstruction placed maize <i>BIF1</i> in a clade sister to <i>Arabidopsis thaliana AtIAA15</i>. The <i> BIF1</i> lineage has undergone two gene duplications since the divergence of the early grasses. Molecular evolutionary analyses by maximum likelihood suggest that the <i>BIF1</i> alignment is under strong purifying selection with positive selection acting on a glutamine residue located in a functional region associated with <i>AUX/IAA</i> protein dimerization in one clade of <i>BIF1</i> paralogs, the <i>BIF1-Like2</i> (<i>BIF1L2</i>) clade. A character reconstruction analysis using maximum parsimony estimated an adenine to cytosine transversion at the base of the <i>BIF1L2</i> clade changed a glutamine into an alanine residue in this functional region. Expression of <i>BIF1</i> orthologs is conserved in floral meristems in the eudicot <i>AtIAA15</i> clade containing the taxa <i>Erianthe Guttata, Arabidopsis thaliana, Medicago truncatula</i>, however grass <i>BIF1L2</i> expression has diverged within the PACMAD – BEP clade, specifically in rice, where <i> BIF1L2</i> expression is reported to have moved into root tissue. These results suggest that <i>BIF1</i> paralogs has changed following a second round of gene duplication in the grasses. Taken together, a change in localized expression in these sequences, and positive selection acting on a glutamine-rich region of the protein-protein binding motif could imply that BARREN INFLORESCENCE1-like2 proteins are probably interacting with a new set or subset of AUXIN RESPONSE FACTOR (ARF) binding partners, and that neofunctionalization has occurred in the <i>BARREN INFLORESCENCE1-like2 </i> clade.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:1527538 |
| Date | 23 April 2014 |
| Creators | Child, Robert Joseph |
| Publisher | California State University, Long Beach |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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