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Inflorescence Development In The Teosinte Zea Luxurians (Poaceae) And Implication For The Origin Of Maize Inflorescences

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Cross-sex transfer, Homeosis, Inflorescence development, Maize evolution, Teosinte, Z. luxurians

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Scanning electron microscopy observations of tassel and ear development in a primitive form of annual teosinte, Zea luxurians, were consistent with the hypothesis that, phylogenetically, femininity and masculinity in cultivated maize and teosinte were derived from a common developmental background. Branch primordia were initiated in a distichous phyllotaxy along the inflorescence rachis. Spikelet primordia were derived from branch primordia and subsequently bifurcated into pedicellate and sessile spikelets. Pedicellate spikelets were aborted in the female inflorescences, but were functional in the male inflorescences. Male and female floret development in Z. luxurians was similar to that described for other teosintes, landrace maize, cultivated maize and gamagrass. However, some lateral primary branches of Z. luxurians produced terminal inflorescences which exhibited novel teosinte tassel orthostichies: two/four (distichous/quadristichous) and two/three (distichous/tristichous) phyllotaxy combinations, and a putative mixed-zone (female/male) condition. Furthermore, novel four-rowed female spikelets (due to paired spikelets) were observed in some Z. luxurians mixed-zone terminal lateral primary inflorescences. The polystichous inflorescence phenotype in Z. luxurians supports the hypothesis that the maize ear evolved by the appearance of polystichous phenotypes in teosinte primary lateral branches. These results also are consistent with the hypothesis that the maize ear was derived from a homeotic cross-sex transition in a male teosinte inflorescence that terminated the lateral primary branches. In addition, a few presumptive female inflorescences exhibited a morphological state (female/male) that showed a homeotic cross-sex transfer. We revealed novel phenotypes of partially feminized LA 2 tassels that exhibited either a polystichous phenotype or a four-rowed female spikelet phenotype.


Department of Biology

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