Understanding the classical maize floral development mutant, Polytypic ear1

Abstract

Maize produces two inflorescences, the tassel and ear, which are critical for both plant reproduction and agriculture. The classical semi-dominant mutant, Polytypic ear1 (Pt1), affects multiple aspects of inflorescence development, including floral development. Pt1 heterozygote ears and tassels appear to have barren tips with extra floral organs towards the base with extra silks or branch-like protrusions. While the causative gene is unknown, RNA-seq provided direction for candidate gene analysis. Our top candidate gene, ethylene response sensor1 (ers1), encodes a putative ethylene receptor that shows allele-specific expression in Pt1. Ethylene receptors negatively regulate ethylene signaling, and in Arabidopsis, dominant mutations confer ethylene insensitivity. I hypothesized that overexpression of ethylene receptors may also confer a similar ethylene insensitive phenotype. To test this hypothesis, I evaluated ethylene sensitivity of Pt1 mutants. Pt1/+ siblings had no significant difference in growth in the presence and absence of the ethylene precursor ACC, but these results are not conclusive due to lack of robust wildtype results. While the ers1 RNA in situ hybridization failed to detect ers1 transcripts, the in situs of genes expressed in the boundary between upper and lower florets were similar in normal and Pt1/+ plants. The pectin localization patterns of Pt1/+ plants differed from normal siblings suggesting that floral meristem determinacy could be linked to changes in cell wall dynamics.