RESUMO
Native Americans domesticated maize (Zea mays ssp. mays) from lowland teosinte parviglumis (Zea mays ssp. parviglumis) in the warm Mexican southwest and brought it to the highlands of Mexico and South America where it was exposed to lower temperatures that imposed strong selection on flowering time. Phospholipids are important metabolites in plant responses to low-temperature and phosphorus availability and have been suggested to influence flowering time. Here, we combined linkage mapping with genome scans to identify High PhosphatidylCholine 1 (HPC1), a gene that encodes a phospholipase A1 enzyme, as a major driver of phospholipid variation in highland maize. Common garden experiments demonstrated strong genotype-by-environment interactions associated with variation at HPC1, with the highland HPC1 allele leading to higher fitness in highlands, possibly by hastening flowering. The highland maize HPC1 variant resulted in impaired function of the encoded protein due to a polymorphism in a highly conserved sequence. A meta-analysis across HPC1 orthologs indicated a strong association between the identity of the amino acid at this position and optimal growth in prokaryotes. Mutagenesis of HPC1 via genome editing validated its role in regulating phospholipid metabolism. Finally, we showed that the highland HPC1 allele entered cultivated maize by introgression from the wild highland teosinte Zea mays ssp. mexicana and has been maintained in maize breeding lines from the Northern United States, Canada, and Europe. Thus, HPC1 introgressed from teosinte mexicana underlies a large metabolic QTL that modulates phosphatidylcholine levels and has an adaptive effect at least in part via induction of early flowering time.
Assuntos
Adaptação Fisiológica , Flores , Interação Gene-Ambiente , Fosfatidilcolinas , Fosfolipases A1 , Proteínas de Plantas , Zea mays , Alelos , Mapeamento Cromossômico , Flores/genética , Flores/metabolismo , Genes de Plantas , Ligação Genética , Fosfatidilcolinas/metabolismo , Fosfolipases A1/classificação , Fosfolipases A1/genética , Fosfolipases A1/metabolismo , Proteínas de Plantas/classificação , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Zea mays/genética , Zea mays/crescimento & desenvolvimentoRESUMO
Determining the in situ pattern of protein expression is crucial to accurately establish regulatory function and mode of action of any plant developmental program. Here, we describe two immunolocalization procedures that are consistently used to determine subcellular localization of ARGONAUTE proteins in the ovule of the Brassicaceae. The first is performed in resin-embedded semi-thin sections of developing ovules that can be observed under bright-field microscopy. The second is based in polyacrylamide immersion of complete (whole-mounted) gynoecia or ovules that are observed under confocal microscopy. Both procedures have been successfully performed to localize proteins involved in RNA-directed DNA methylation during the development of the anatropous bitegmic ovule in Arabidopsis, Brassica, or Boechera species.
Assuntos
Arabidopsis/genética , Proteínas Argonautas/genética , Regulação da Expressão Gênica no Desenvolvimento/genética , Óvulo Vegetal/genética , Proteínas de Arabidopsis/genética , Metilação de DNA/genética , Regulação da Expressão Gênica de Plantas/genéticaRESUMO
Female gametogenesis in most flowering plants depends on the predetermined selection of a single meiotically derived cell, as the three other megaspores die without further division or differentiation. Although in Arabidopsis thaliana the formation of the functional megaspore (FM) is crucial for the establishment of the gametophytic generation, the mechanisms that determine the specification and fate of haploid cells remain unknown. Here, we show that the classical arabinogalactan protein 18 (AGP18) exerts an active regulation over the selection and survival of megaspores in Arabidopsis. During meiosis, AGP18 is expressed in integumentary cells located in the abaxial region of the ovule. Overexpression of AGP18 results in the abnormal maintenance of surviving megaspores that can acquire a FM identity but is not sufficient to induce FM differentiation before meiosis, indicating that AGP18 positively promotes the selection of viable megaspores. We also show that all four meiotically derived cells in the ovule of Arabidopsis are competent to differentiate into a gametic precursor and that the function of AGP18 is important for their selection and viability. Our results suggest an evolutionary role for arabinogalactan proteins in the acquisition of monospory and the developmental plasticity that is intrinsic to sexual reproduction in flowering plants.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Glicoproteínas de Membrana/genética , Óvulo Vegetal/genética , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Gametogênese Vegetal/genética , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Glucuronidase/genética , Glucuronidase/metabolismo , Meiose/genética , Glicoproteínas de Membrana/metabolismo , Microscopia de Fluorescência , Mucoproteínas/genética , Mucoproteínas/metabolismo , Óvulo Vegetal/crescimento & desenvolvimento , Óvulo Vegetal/metabolismo , Plantas Geneticamente Modificadas , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
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 in flowering plants. In this review, we discuss recent findings indicating that epigenetic mechanisms related to the activity of small RNA pathways prevailing during ovule formation play an essential role in cell specification and genome integrity. We also compare these findings to small RNA pathways acting during gametogenesis in animals and discuss their implications for the understanding of the mechanisms that control the establishment of the female gametophytic lineage during both sexual reproduction and apomixis.