Abstract
Agave tequilana is an angiosperm species that belongs to the family Asparagaceae (formerly Agavaceae). Even though there is information regarding to some aspects related to the megagametogenesis of A. tequilana, this is the first report describing the complete process of megasporogenesis, megagametogenesis, the early embryo and endosperm development process in detail. The objective of this work was to study and characterize all the above processes and the distinctive morphological changes of the micropylar and chalazal extremes after fertilization in this species. The agave plant material for the present study was collected from commercial plantations in the state of Jalisco, Mexico. Ovules and immature seeds, previously fixed in FAA and kept in ethanol 70%, were stained based on a tissue clarification technique by using a Mayer’s-Hematoxylin solution. The tissue clarification technique was successfully used for the characterization of the megasporogenesis, megagametogenesis, mature embryo sac formation, the early embryo and endosperm development processes by studying intact cells. The embryo sac of A. tequilana was confirmed to be of the monosporic Polygonum-type and an helobial endosperm formation. Also, the time-lapse of the developmental processes studied was recorded.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-3-575) contains supplementary material, which is available to authorized users.
Highlights
One of the main characteristics of Angiosperms is that they possess seeds enclosed inside a fruit derived from the ovary of flowers (Li and Ma 2002)
The embryo sacs may present a diversity of developmental pathways, the most common is the monosporic Polygonum-type, in which the functional megaspore passes through three mitotic divisions producing a seven celled embryo sac (Chasan and Walbot 1993; Li and Ma 2002; Maheshwari 1937) consisting of three antipodal cells, one central cell formed by two polar nuclei, two synergid cells, and the egg cell (Dresselhaus 2006; Kägi and Groß-Hardt 2007; Yang et al 2010)
The objective of this work was to study and characterize the process of megasporogenesis, megagametogenesis, the mature embryo sac formation and the early embryo development in Agave tequilana Weber which is the raw material for the production of Tequila in Mexico, in order to get basic knowledge useful for plant systematics and evolution studies and plant breeding programs, which may include in vitro fertilization and the production of haploid plants among others
Summary
One of the main characteristics of Angiosperms is that they possess seeds enclosed inside a fruit derived from the ovary of flowers (Li and Ma 2002) Another outstanding characteristic of angiosperms is that they present alternation of generations in their life cycle (as in many other plants), that is divided in two phases: one dominant diploid phase, which is called sporophytic, and one haploid phase known as gametophytic (Haig 1990; RodríguezGaray et al 2000; Fan et al 2008; Ma and Sundaresan 2010). The embryo sacs may present a diversity of developmental pathways, the most common is the monosporic Polygonum-type, in which the functional megaspore passes through three mitotic divisions producing a seven celled embryo sac (Chasan and Walbot 1993; Li and Ma 2002; Maheshwari 1937) consisting of three antipodal cells, one central cell formed by two polar nuclei, two synergid cells, and the egg cell (Dresselhaus 2006; Kägi and Groß-Hardt 2007; Yang et al 2010)
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