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Emergence and patterning of the five cell types of the Zea mays anther locule.

ABSTRACT: One fundamental difference between plants and animals is the existence of a germ-line in animals and its absence in plants. In flowering plants, the sexual organs (stamens and carpels) are composed almost entirely of somatic cells, a small subset of which switch to meiosis; however, the mechanism of meiotic cell fate acquisition is a long-standing botanical mystery. In the maize (Zea mays) anther microsporangium, the somatic tissues consist of four concentric cell layers that surround and support reproductive cells as they progress through meiosis and pollen maturation. Male sterility, defined as the absence of viable pollen, is a common phenotype in flowering plants, and many male sterile mutants have defects in somatic and reproductive cell fate acquisition. However, without a robust model of anther cell fate acquisition based on careful observation of wild-type anther ontogeny, interpretation of cell fate mutants is limited. To address this, the pattern of cell proliferation, expansion, and differentiation was tracked in three dimensions over 30 days of wild-type (W23) anther development, using anthers stained with propidium iodide (PI) and/or 5-ethynyl-2'-deoxyuridine (EdU) (S-phase label) and imaged by confocal microscopy. The pervading lineage model of anther development claims that new cell layers are generated by coordinated, oriented cell divisions in transient precursor cell types. In reconstructing anther cell division patterns, however, we can only confirm this for the origin of the middle layer (ml) and tapetum, while young anther development appears more complex. We find that each anther cell type undergoes a burst of cell division after specification with a characteristic pattern of both cell expansion and division. Comparisons between two inbreds lines and between ab- and adaxial anther florets indicated near identity: anther development is highly canalized and synchronized. Three classical models of plant organ development are tested and ruled out; however, local clustering of developmental events was identified for several processes, including the first evidence for a direct relationship between the development of ml and tapetal cells. We speculate that small groups of ml and tapetum cells function as a developmental unit dedicated to the development of a single pollen grain.

SUBMITTER: Kelliher T

PROVIDER: S-EPMC3024885 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Emergence and patterning of the five cell types of the Zea mays anther locule.

Kelliher Timothy T Walbot Virginia V

Developmental biology 20101109 1

One fundamental difference between plants and animals is the existence of a germ-line in animals and its absence in plants. In flowering plants, the sexual organs (stamens and carpels) are composed almost entirely of somatic cells, a small subset of which switch to meiosis; however, the mechanism of meiotic cell fate acquisition is a long-standing botanical mystery. In the maize (Zea mays) anther microsporangium, the somatic tissues consist of four concentric cell layers that surround and suppor ...[more]

PMID: 21070762

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Project description:Maize tassel is the male reproductive organ which is located at the plant's apex; both its morphological structure and fertility have a profound impact on maize grain yield. More than 40 functional genes regulating the complex tassel traits have been cloned up to now. However, the detailed molecular mechanisms underlying the whole process, from male inflorescence meristem initiation to tassel morphogenesis, are seldom discussed. Here, we summarize the male inflorescence developmental genes and construct a molecular regulatory network to further reveal the molecular mechanisms underlying tassel-trait formation in maize. Meanwhile, as one of the most frequently studied quantitative traits, hundreds of quantitative trait loci (QTLs) and thousands of quantitative trait nucleotides (QTNs) related to tassel morphology have been identified so far. To reveal the genetic structure of tassel traits, we constructed a consensus physical map for tassel traits by summarizing the genetic studies conducted over the past 20 years, and identified 97 hotspot intervals (HSIs) that can be repeatedly mapped in different labs, which will be helpful for marker-assisted selection (MAS) in improving maize yield as well as for providing theoretical guidance in the subsequent identification of the functional genes modulating tassel morphology. In addition, maize is one of the most successful crops in utilizing heterosis; mining of the genic male sterility (GMS) genes is crucial in developing biotechnology-based male-sterility (BMS) systems for seed production and hybrid breeding. In maize, more than 30 GMS genes have been isolated and characterized, and at least 15 GMS genes have been promptly validated by CRISPR/Cas9 mutagenesis within the past two years. We thus summarize the maize GMS genes and further update the molecular regulatory networks underlying male fertility in maize. Taken together, the identified HSIs, genes and molecular mechanisms underlying tassel morphological structure and male fertility are useful for guiding the subsequent cloning of functional genes and for molecular design breeding in maize. Finally, the strategies concerning efficient and rapid isolation of genes controlling tassel morphological structure and male fertility and their application in maize molecular breeding are also discussed.

Project description:BackgroundHealth risks arising from heavy metal pollution have attracted global attention. As a result, many studies on the accumulation of heavy metals in soil-plant systems have performed human health risk assessments.ObjectivesWe aimed to examine the ability of Zea mays (maize) to accumulate heavy metals and assess the bioaccumulation factor (BAF) by collecting, collating, and analyzing data on heavy metal concentrations in Zea mays.MethodsThis study reviewed the accumulation of five selected heavy metals, cadmium (Cd), chromium (Cr), lead (Pb), copper (Cu), and zinc (Zn) in soil and the corresponding BAF of Zea mays grown on those soils using a systematic search of peer-reviewed scientific journals. A total of 27 research works were reviewed after screening 52 articles for subject matter relevancy, including dumpsites, industrially polluted soils, inorganically fertilized soils, mining sites, smelting sites, municipal wastewater irrigated soils, and a battery waste dumpsite.ResultsAmong the reviewed sites, concentrations of Cd and Cr were highest at a tin mining site, where prolonged mining, mineral processing and other production activities contributed heavy metal pollution in the soil. The soil at a battery waste dumpsite exhibited the highest Pb concentration, while the soil at a Zn smelting site presented the highest concentration of Zn. The highest soil Cu concentration was found in an area where sewage irrigation had been carried out over a long period. The BAF of the five heavy metals in Zea mays increased with the metal concentrations in the soil. The BAF of Cd, Cr, Pb, Cu, and Zn in Zea mays from the study areas fall within the ranges of 0-0.95, 0-1.89, 0-1.20, 0.011-0.99, and 0.03-0.99, respectively. Cadmium and Zn had the highest bioconcentration factors values in maize plants, likely due to their higher mobility rate compared to the other heavy metals.ConclusionsThe study concluded that Zea mays is capable of accumulating high amounts of heavy metals, although accumulation of these heavy metals is influenced by multiple factors including soil texture, cation exchange capacity, root exudation and especially soil pH and chemical forms of the heavy metals. Zea mays should not be planted on metal-contaminated soils because of its potential to act as a hyperaccumulator.Competing interestsThe authors declare no competing financial interests.

Dataset Information

Emergence and patterning of the five cell types of the Zea mays anther locule.

Publications

Emergence and patterning of the five cell types of the Zea mays anther locule.

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