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Group of Reproductive Development and Apomixis


Group of Reproductive Development and Apomixis

  • Female reproductive development.

The female gametophyte of Arabidopsis is contained within the ovule and is composed of seven cells: 3 antipodals, 2 synergids, the egg cell, and a binucleated central cell. MPSS is a large-scale sequencing technology that generates 21 nt. signature tags corresponding to transcripts that can be assigned to their genomic location, allowing the quantitative estimation of gene expression. Our lab developed a microaspirator-based strategy for ovule harvesting that allows the isolation of ~12 mg of total RNA in 2 hours. The technology was used to generate large collections of 21 nt mRNA-derived or non-coding RNA (ncRNA)-derived Massively Parallel Signature Sequencing (MPSS) tags in both wild-type and mutants lacking a female gametophyte within the ovule. The strategy allowed the identification of the largest collection of genes expressed in either the ovule or the female gametophyte, including small ncRNAs with important regulatory roles in female reproductive development. This large effort now represents the initial platform for many developmental projects in our lab, including the characterization of specific protein families, microRNAs, and genes representing maternal factors acting during early seed development. The overall results are important to globally analyse the transcriptional universe present in the ovule prior to double fertilization.

  • How does a somatic cell becomes a plant embryo? Epigenetic control of gametogenesis and seed formation.

The problem has puzzled plant biologists for more than a 100 years. Although many other questions have the potential to completely transform our current view of agricultural biotechnology, it is believed that the solution to this particular one has a unique potential to impact multiple biological areas (“What don’t we know?”. Science 309: 75). In flowering plants, the formation of gametes depends on the differentiation of cellular precursors that divide meiotically before giving rise to a multicellular gametophyte. The establishment of this gametophytic phase presents an opportunity for natural selection to act on the haploid plant genome by means of epigenetic mechanisms that ensure a tight regulation of plant reproductive development. Despite this early acting selective pressure, there are numerous examples of naturally occurring developmental alternatives that suggest a flexible regulatory control of cell specification and subsequent gamete formation.

It is becoming clear that the genetic control of female gametogenesis and seed formation is directed by epigenetic mechanisms that are crucial to direct the developmental events that distinguish sexual from asexual embryo formation in the ovule (Olmedo-Monfil et al., 2010). A global elucidation of some of these mechanisms and their consequences is the main objective of this proposal. Understanding asexual reproduction through embryos should lead to sorting out the cellular switches that plants use to maintain a remarkable developmental plasticity while still keeping a strict control over growth. We expect that results from this proposal will substantially contribute to understand the fundamental mechanisms that cause apomixis in a plant ovule. The long term objective of research in our laboratory remains to explore the possibilities of inducing apomixis in a sexual flowering plant.

  • The origins of maize and its domestication.

The genome of the mexican Palomero toluqueño landrace was characterized in our institution. Based on cytogenetic studies by A. Kato and B. McClintock, Palomero toluqueño is one of a few landraces believed to form an ancient group of primitive maize that spread through the Pacific Coast from domestication sites in the Tehuacán Valley to Northern Mexico and the United States.

These genomic analysis is being used as a platform to identify new domestication genes. In addition to new members of gene families encoding sugar metabolic enzymes or auxin response transcription factors that were previously identified as affected by artificial selection, we also identified 3 domestication genes encoding proteins involved in heavy metal response. At least 10 other genomic regions containing genes encoding proteins involved in abiotic stress and metal response are included in additional non-polymorphic elements that have yet to be tested for domestication. Overall, these results strongly indicate that heavy metal response represents an additional driving force acting on maize domestication. Our group is currently investigating the potential effects that the environment had on the origin of maize, by working with a multidisciplinary team that includes geologists, archeologists, botanists, and ecologists of several institutions in Mexico.

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