TheSTUDGene Is Required for Male-Specific Cytokinesis after Telophase II of Meiosis inArabidopsis thaliana

AbstractDuring male meiosis in wild-typeArabidopsisthe pollen mother cell (PMC) undergoes two meiotic nuclear divisions in the absence of cell division. Only after telophase II is a wall formed which partitions the PMC into four microspores. Each microspore undergoes two subsequent mitotic divisions to produce one vegetative cell and two sperm cells in the mature pollen grain. In this paper we describe the isolation and the phenotypic characterization of mutations in theSTUD(STD) gene, which is specifically required for male-specific cytokinesis after telophase II of meiosis. Although the male meiotic nuclear divisions are normal instdmutant plants, no walls are formed resulting in a tetranucleate microspore. Despite the absence of cell division in the PMC, postmeiotic development in the coenocytic microspore proceeds relatively normally, resulting in the formation of large pollen grains which contain four vegetative nuclei and up to eight sperm cells. Interestingly, these enlarged pollen grains which contain multiple vegetative nuclei and extra sperm cells behave as single male gametophytes, producing only single pollen tubes and resulting in partial male fertility instdmutant plants. Characterization of the process of pollen development and pollen function instdmutants thus reveals two different types of developmental regulation. Each of the four nuclei found in astdmicrospore following meiosis is capable of independently undergoing the complete mitotic cell division (including cytokinesis) which the single nucleus of a wild-type microspore would normally undertake. The ability of the four meiotic products to independently continue through mitosis does not depend on their division into separate cells, but is controlled by some subcellular component found within the coenocytic micropsore. By contrast, the maturestdpollen grain functions as a unit and produces only a single pollen tube despite the presence of multiple nuclei within the vegetative cell, suggesting that this process is controlled at the cellular level independently of the extra subcellular components

L’impact de la grossesse sur l’amplitude et la diversité de la reconnaissance antigénique des lymphocytes T cytotoxiques dirigés contre le VIH-1

La transmission mère-enfant (TME) du VIH-1 est un des enjeux majeurs de la pandémie. Une meilleure compréhension de la réponse des lymphocytes T cytotoxiques CD8+ (LTC) VIH-spécifiques lors de la grossesse facilitera le design de stratégies optimales pour diminuer la TME. Notre objectif est donc de caractériser l’amplitude et la diversité de la reconnaissance antigénique des LTC VIH-spécifiques avant, pendant et après la grossesse chez des femmes infectées par le VIH-1. Nos résultats montrent pour la première fois que l’initiation et la progression de la grossesse, à elles seules, n'ont que peu d’influence sur l’amplitude et la diversité de la reconnaissance antigénique des réponses LTC en termes de production d’IFN‐. Ces résultats indiquent que les femmes infectées par le VIH conservent une immunocompétence durant leur grossesse, du moins dans le contexte d’un traitement antirétroviral efficace. Ceci pourrait éventuellement aider à promouvoir l’immunisation comme stratégie pour prévenir la TME du VIH‐1.Mother-to-child transmission (MTCT) of HIV-1 is one of the major issues of the pandemic. Characterization of HIV-specific immunity during pregnancy, especially cytotoxic CD8+ T lymphocytes (CTL), will lead to a better understanding of HIV pathogenesis and facilitate design of optimal strategies to prevent MTCT. Our objective is to describe the magnitude and the breadth of antigen recognition of HIV-specific CTL responses before, throughout and after pregnancy in a group of HIV-infected women. Our results revealed for the first time that initiation of pregnancy by itself doesn’t change the magnitude of CTL responses in terms of IFN- production. These findings support the fact that HIV-infected women maintain immunocompetence throughout gestation, at least in the context of effective antiretroviral treatment. These results provide a novel understanding of the dynamics of HIV-specific CTL responses during pregnancy and may help to promote maternal immunization as a strategy to prevent MTCT of HIV-1

FIDDLEHEAD, a gene required to suppress epidermal cell interactions in Arabidopsis, encodes a putative lipid biosynthetic enzyme

In plants, the outer epidermal cell wall and cuticle presents a semipermeable barrier that maintains the external integrity of the plant and regulates the passage of various classes of molecules into and out of the organism. During vegetative development, the epidermal cells remain relatively inert, failing to respond to wounding or grafting. During reproductive development and fertilization, however, the epidermis is developmentally more labile and participates in two types of contact-mediated cell interactions: organ fusion and pollen hydration. Here we describe the isolation and characterization of one gene whose product normally functions in blocking both types of epidermal cell interactions during vegetative development: the FIDDLEHEAD gene. As suggested by previous biochemical analyses, the gene encodes a protein that is probably involved in the synthesis of long-chain lipids found in the cuticle and shows similarity to a large class of genes encoding proteins related to β-ketoacyl-CoA synthases and chalcone synthases. In situ hybridization reveals an epidermal pattern of expression consistent with a role for this protein in the synthesis of lipid components that are thought to localize extracellularly and probably modify the properties of the cuticle

Developmental Regulation of Cell Interactions in theArabidopsis fiddlehead-1Mutant: A Role for the Epidermal Cell Wall and Cuticle

AbstractAlthough the plant epidermis serves primarily a protective role, during plant development some epidermal cells specialize, becoming competent to interact not only with pollen but also with other epidermal cells. In the former case, these interactions mediate recognition, germination, and pollen growth responses and, in the latter case, result in interorgan fusions which, most commonly, alter floral architecture in ways that are thought to promote reproductive success. In either case, all of the initial signaling events must take place across the cell wall and cuticle. InArabidopsis,mutation of theFIDDLEHEADgene alters the shoot epidermis such that all epidermal cells become competent to participate in both types of interactions. Infdh-1mutants, epidermal cells manifest not only a contact-mediated fusion response but also interact with pollen. Since carpel epidermal derivatives manifest both of these properties, we postulated thatfdh-1epidermal cells were ectopically expressing a carpel-like program. In this report we demonstrate that manifestation of thefdh-1phenotype does not require the product of theAGAMOUSgene, indicating that the phenotype is either independent of the carpel development program or thatfdh-1mutations activate a carpel-specific developmental program downstream of theAGgene. Furthermore, we demonstrate that plants bearing mutations in thefdh-1gene show significant changes in cell wall and cuticular permeability. Biochemical analyses of the lipid composition of the crude cell wall fraction reveal thatfdh-1cell walls differ from wild-type and manifest significant changes in high-molecular-weight lipid peaks. These results suggest that cell wall and cuticular permeability may be important determinants in developmental signaling between interacting cells and implicate lipids as important factors in modulating the selectivity of the permeability barrier presented by the epidermal cell wall and cuticle

Colx194E9, F1 #5, plant 54 raw data, T14G11 indel marker.

<p>T14G11 indel marker initial data analysis of qPCR results.</p

LC13, wt hybrid plants 9B-10B raw data, T14G11 indel marker.

<p>T14G11 indel marker initial data analysis of qPCR results.</p

Colx194E9, F1 #5, plant 54 raw data, F15H11 indel marker.

<p>F15H11 indel marker initial data analysis of qPCR results.</p

Colx194E9, F1 #5, plant 54 raw data, T6H20 indel marker.

<p>T6H20 indel marker initial data analysis of qPCR results.</p