Analysis of inflorescence organogenesis in eastern gamagrass, Tripsacum dactyloides (Poaceae): the wild type and the gynomonoecious gsf1 mutant

Abstract

Inflorescence organogenesis of a wild-type and a gynomonoecious (pistillate) mutant in Tripsacum dactyloides was studied using scanning electron microscopy. SEM (scanning electron microscope) analysis indicated that wild-type T. dactyloides (Eastern gamagrass) expressed a pattern of inflorescence organogenesis that is observed in other members of the subtribe Tripsacinae (Zea: maize and teosinte), family Poaceae. Branch primordia are initiated acropetally along the rachis of wild-type inflorescences in a distichous arrangement. Branch primordia at the base of some inflorescences develop into long branches, which themselves produce an acropetal series of distichous spikelet pair primordia. All other branch primordia function as spikelet pair primordia and bifurcate into pedicellate and sessile spikelet primordia. In all wild-type inflorescences development of the pedicellate spikelets is arrested in the proximal portion of the rachis, and these spikelets abort, leaving two rows of solitary sessile spikelets. Organogenesis of spikelets and florets in wild-type inflorescences is similar to that previously described in maize and the teosintes. Our analysis of gsf1 mutant inflorescences reveals a pattern of development similar to that of the wild type, but differs from the wild type in retaining (1) the pistillate condition in paired spikelets along the distal portion of the rachis and (2) the lower floret in sessile spikelets in the proximal region of the rachis. The gsf1 mutation blocks gynoecial tissue abortion in both the paired-spikelet and the unpaired-spikelet zone. This study supports the hypothesis that both femaleness and maleness in Zea and Tripsacum inflorescences are derived from a common developmental pathway. The pattern of inflorescence development is not inconsistent with the view that the maize ear was derived from a Tripsacum genomic background.

Inflorescence development in a high‐altitude annual Mexican teosinte (Poaceae)

“…parviglumis and subsp. This developmental marker is also found in Tripsacum inflorescences (Orr et al, 2001). Fig.…”

“…25 in Orr and Sundberg, 1994a). The codification of the inflorescence branching pattern in Tripsacum, another member of the Tripsacinae, is similar to the axial designation used in this paper (Orr et al, 2001). The codification of the inflorescence branching pattern in Tripsacum, another member of the Tripsacinae, is similar to the axial designation used in this paper (Orr et al, 2001).…”

“…Nonabortive spikelet primordia of Toluca teosinte developed additional primordia chronometrically-outer glume, inner glume, outer lemma, lower floret, inner lemma, upper floret, and palea-in a sequential pattern common to other teosintes, maizes, and Eastern gamagrass (Orr et al, 2001). Both the upper and lower florets of these functional spikelets produced stamen and ovule primordia.…”

“…One unresolved issue in the controversy of maize evolution is the origin of the maize ear, which has sparked developmental investigation (Orr et al, 2001). Previous studies of inflorescence development in the genera Tripsacum and Zea (teosintes and maize; Poaceae: Andropogoneae) have shown a developmental pattern common to the ears and tassels of teosinte (Sundberg andOrr, 1986, 1990;Sundberg, 1987;Orr and Sundberg, 1994a, b), small-eared ''primitive'' maizes (Sundberg, LaFargue, and Orr, 1995;Sundberg and Orr, 1996), and eastern gamagrass, T. dactyloides (L.) L. (Orr et al, 2001). Both femininity and masculinity were derived from a common developmental background, although key variations have been uncovered that differentiate teosinte inflorescences from maize inflorescences and Zea ears from Zea tassels (Orr and Sundberg, 1994a).…”

Development and Structure of the Grass Inflorescence

“…In grasses, the pair of spikelets is a shBr that produces a single lateral meristem and then terminates in a spikelet. The sessile spikelet is lateral and the pedicellate one is terminal (Cámara Hernández & Gambino, 1990;Vegetti, 1994Vegetti, , 1999Irish, 1997Irish, , 1998Orr et al, 2001;Gallavotti et al, 2004;Vollbrecht et al, 2005;Bortiri et al, 2006;Wu and McSteen, 2007). In the Paniceae tribe, which is sister to Andropogoneae, most species have single spikelets, but a few species produce paired spikelets (Rua & Weberling, 1998;Kellogg, 2000;Kellogg et al 2004;Reinheimer, 2007;Reinheimer & Vegetti, 2008).…”