Auxin is a phytohormone that has long been known to control many aspects of plant growth and development. The YUCCA (YUC) gene family is a large group of genes that catalyze auxin biosynthesis and have been shown to be critical for vegetative growth and inflorescence development in grasses. There is genetic redundancy present with Arabidopsis YUCs, but in Zea mays (maize), a single gene knockout of ZmSPI1 causes a severe inflorescence phenotype. Since Oryza sativa (rice), another grass species, does not show an inflorescence phenotype when OsYUC1/SPI1 is knocked down, SPI1 appears to have undergone an evolutionary shift in function within the grass family. This study shows that SPI1 expression in PACMAD (Panicoideae, Arundinoideae, Chlorodoideae, Micrairoideae, Aristidoideae, and Danthoniodeae subfamilies) clade grasses Sorghum bicolor and Setaria italica occurs at sites of inflorescence branching and is consistent with maize, but in BEP (Bambusoideae, Ehrhartoideae, and Pooideae subfamilies) clade grasses rice and Brachypodium distachyon SPI1 shifts from localized expression to more generalized expression and potentially becomes weaker. Artificial microRNA (amiRNA) knockdowns of SPI1 expression in Brachypodium did not show a phenotype when expression was reduced to 28.01% (+/- 6.39%) of wild type. In rice and Brachypodium, other YUC genes were shown to be expressed in the inflorescence by quantitative RT-PCR (qPCR), suggesting YUC proteins are more redundant in BEP grasses such as B. distachyon and O. sativa, than in maize and potentially its relatives.
|Commitee:||Brusslan, Judith, Haas-Stapleton, Eric|
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 52/01M(E), Masters Abstracts International|
|Subjects:||Molecular biology, Plant biology, Genetics|
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