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At least 865 records · Page 48Linked to original sources
PubMed2006

Ethylene sensing and gene activation in Botrytis cinerea: a missing link in ethylene regulation of fungus-plant interactions?

Ethylene production by infected plants is an early resistance response leading to activation of plant defense pathways. However, plant pathogens also are capable of producing ethylene, and ethylene might have an effect not only on the plant but on the pathogen as well. Therefore, ethylene may play a dual role in fungus-plant interactions by affecting the plant as well as the pathogen. To address this question, we studied the effects of ethylene on the gray mold fungus Botrytis cinerea and the disease it causes on Nicotiana benthamiana plants. Exposure of B. cinerea to ethylene inhibited mycelium growth in vitro and caused transcriptional changes in a large number of fungal genes. A screen of fungal signaling mutants revealed a Galpha null mutant (deltabcg1) which was ethylene insensitive, overproduced ethylene in vitro, and showed considerable transcriptional changes in response to ethylene compared with the wild type. Aminoethoxyvinylglycine (AVG)-treated, ethylene-nonproducing N. benthamiana plants developed much larger necroses than ethylene-producing plants, whereas addition of ethylene to AVG-treated leaves restricted disease spreading. Ethylene also affected fungal gene expression in planta. Expression of a putative pathogenicity fungal gene, bcspl1, was enhanced 24 h after inoculation in ethylene-producing plants but only 48 h after inoculation in ethylene-nonproducing plants. Our results show that the responses of B. cinerea to ethylene are partly mediated by a G protein signaling pathway, and that ethylene-induced plant resistance might involve effects of plant ethylene on both the plant and the fungus.

Amino Acid Sequence↗
PubMed2003

Hormonal control of cell proliferation requires PASTICCINO genes.

PASTICCINO (PAS) genes are required for coordinated cell division and differentiation during plant development. In loss-of-function pas mutants, plant aerial tissues showed ectopic cell division that was specifically enhanced by cytokinins, leading to disorganized tumor-like tissue. To determine the role of the PAS genes in controlling cell proliferation, we first analyzed the expression profiles of several genes involved in cell division and meristem function. Differentiated and meristematic cells of the pas mutants were more competent for cell division as illustrated by the ectopic and enlarged expression profiles of CYCLIN-DEPENDENT KINASE A and CYCLIN B1. The expression of meristematic homeobox genes KNOTTED-LIKE IN ARABIDOPSIS (KNAT2, KNAT6), and SHOOT MERISTEMLESS was also increased in pas mutants. Moreover, the loss of meristem function caused by shoot meristemless mutation can be suppressed by pas2. The KNAT2 expression pattern defines an enlarged meristematic zone in pas mutants that can be mimicked in wild type by cytokinin treatment. Cytokinin induction of the primary cytokinin response markers, ARABIDOPSIS RESPONSE REGULATOR (ARR5 and ARR6), was enhanced and lasted longer in pas mutants, suggesting that PAS genes in wild type repress cytokinin responses. The expression of the cytokinin-regulated cyclin D, cyclin D3.1, was nonetheless not modified in pas mutants. However, primary auxin response genes were down-regulated in pas mutants, as shown by a lower auxin induction of IAA4 and IAA1 genes, demonstrating that the auxin response was also modified. Altogether, our results suggest that PAS genes are involved in the hormonal control of cell division and differentiation.

Arabidopsis↗
PubMed1992

LEAFY Interacts with Floral Homeotic Genes to Regulate Arabidopsis Floral Development.

In the leafy mutant of Arabidopsis, most of the lateral meristems that are fated to develop as flowers in a wild-type plant develop as inflorescence branches, whereas a few develop as abnormal flowers consisting of whorls of sepals and carpels. We have isolated several new alleles of leafy and constructed a series of double mutants with leafy and other homeotic mutants affecting floral development to determine how these genes interact to specify the developmental fate of lateral meristems. We found that leafy is completely epistatic to pistillata and interacts additively with agamous in early floral whorls, whereas in later whorls leafy is epistatic to agamous. Double mutants with leafy and either apetala1 or apetala2 showed a complete loss of the whorled phyllotaxy, shortened internodes, and suppression of axillary buds typical of flowers. Our results suggest that the products of LEAFY, APETALA1, and APETALA2 together control the differentiation of lateral meristems as flowers rather than as inflorescence branches.

Journal Article↗
PubMed1996

Cell-Specific Expression of Mitochondrial Transcripts in Maize Seedlings.

Although mitochondria are thought to assume crucial and possibly novel physiological functions during male gametogenesis, it is not known to what extent mitochondrial function is necessary for other aspects of plant development or to what degree the expression of plant mitochondrial genes is subject to cell-specific regulation, particularly during vegetative growth. We have used in situ hybridization to show that extensive differences exist in the levels of mitochondrial RNAs (mtRNAs) among different tissues and among different individual cell types within the same organ of maize seedlings. The expression of all examined mtRNAs is enhanced in vascular bundles, particularly in procambium- and xylem-forming cells. Mitochondrial transcript levels correlated highly with cell division activity. For example, in roots, the transcripts are abundant in the dividing cells of the meristem but drop to very low levels in the nondividing cells of the root cap and the meristem quiescent center. By comparison, levels of functional mitochondria, as assessed by rhodamine-123 fluorescence, did not vary greatly among the same group of cells. In shoots, in situ hybridization and blot hybridization revealed differences in the patterns of localization among different mtRNAs. The results indicate that during vegetative growth, mitochondrial gene expression at the transcript level is subject to an unexpected degree of cell-specific regulation and that different controls may operate on different trancripts.

Journal Article↗
PubMed2003

Role of microRNAs in plant and animal development.

Small RNAs, including microRNAs (miRNAs) and short interfering RNAs (siRNAs), are key components of an evolutionarily conserved system of RNA-based gene regulation in eukaryotes. They are involved in many molecular interactions, including defense against viruses and regulation of gene expression during development. miRNAs interfere with expression of messenger RNAs encoding factors that control developmental timing, stem cell maintenance, and other developmental and physiological processes in plants and animals. miRNAs are negative regulators that function as specificity determinants, or guides, within complexes that inhibit protein synthesis (animals) or promote degradation (plants) of mRNA targets.

Animals↗
PubMed2005

Surge and destroy: the role of auxin in plant embryogenesis.

For nearly a century, the plant hormone auxin has been recognized for its effects on post-embryonic plant growth. Now recent insights into the molecular mechanism of auxin transport and signaling are uncovering fundamental roles for auxin in the earliest stages of plant development, such as in the development of the apical-basal (shoot-root) axis in the embryo, as well as in the formation of the root and shoot apical meristems and the cotyledons. Localized surges in auxin within the embryo occur through a sophisticated transcellular transport pathway causing the proteolytic destruction of key transcriptional repressors. As we discuss here, the resulting downstream gene activation, together with other, less well-understood regulatory pathways, establish much of the basic body plan of the angiosperm embryo.

Arabidopsis↗
PubMed1988

CELSS for advanced manned mission.

An overview of the major concepts of Controlled Ecological Life Support System (CELSS) includes an identification of environmental factors, such as gravity levels, light levels, and growth volume, that influence the type of CELSS system that can be developed. Various plant growth systems are described together with their possible space applications. Life support functions performed by plants include food production, atmosphere regeneration, and water purification. Selected relationships between biological and physical-chemical life support techniques are considered as a part of these functions. Consumers in a CELSS may be humans, animals, or microorganisms, but nutritional, water, and atmosphere requirements of humans are emphasized in this report, as they are the primary requirement drivers for a CELSS design. The human role in waste generation is discussed as it affects plant nutrient availability. The role of waste management systems in recovering nutrients for plant growth and requirements for CELSS are defined for air, water, and food. Both physical and a biological nutrient recovery/waste disposal systems are examined. The separate subsystems of a CELSS are identified and discussed. Nutrient recovery, plant irradiation, automation, and facilities equipment and applications are reviewed with special attention to direct solar irradiation using fiber optics. These subsystems, along with other environmental control systems, such as thermal, humidity, and ventilation, are essential to plant growth in the space environment.

Crops, Agricultural↗
PubMed1986

Intoxication of cattle by Perilla frutescens (purple mint).

Perilla frutescens or purple mint has been associated with atypical interstitial pneumonia (AIP) for a quarter of a century. The amount and the stage of the plant required to produce AIP have been much debated. A field case in which catastrophic loses occurred in cattle ingesting hay containing purple mint showed that more than the green plants have the capability of producing atypical interstitial pneumonia. In this study, Perilla frutescens produced atypical interstitial pneumonia in three of five calves to which it was given. The amount required to produce the syndrome ranged from 2.3 to 15.5 kg of green seed stage mint and 11.8 kg of mint hay. The toxic syndromes were similar in signs, but quite different in duration. Necropsy examinations showed varied amounts of pulmonary emphysema and edema. Two of the three affected animals' lungs histologically displayed a marked proliferation of Type II pneumocytes. The flowering or seed parts of perilla mint were found by high pressure liquid chromatographic analysis to contain the highest concentration of perilla ketone, considered the most toxic agent involved. This stage of plant growth was also shown to be the most toxic in our calf feeding trial. Calves fed the flowering plant developed the toxic syndrome while those fed earlier plants (collected before seed stage) and late plants (collected after frost) remained asymptomatic. The time of year when perilla reaches the seed stage often corresponds to periods when pasture grass is scarce forcing cattle to consume plants not normally eaten when ample desirable forage is available.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed2026

Genome-wide characterization of MADS-box genes and their roles in axillary bud development in tobacco.

A total of 118 NtMADS-box genes were identified in tobacco, revealing their potential roles in axillary bud development. Preliminary overexpression analysis indicated that NtMADS91 promotes axillary bud development. MADS-box transcription factors are core regulators of plant development, but their functions in axillary bud development in Nicotiana tabacum L. have not been systematically elucidated. In this study, 118 NtMADS-box genes were identified from the tobacco genome. Phylogenetic analysis classified them into type I (comprising the Mα and Mγ subfamilies) and type II (comprising the MIKC* and MIKCC clades). Promoter analysis revealed that cis-acting elements were predominantly associated with light and hormone responses. RNA-seq analysis of axillary buds after topping identified 60 differentially expressed NtMADS-box genes, from which 12 candidate genes with significant expression changes were selected. Tissue-specific qRT-PCR revealed that seven of these genes were preferentially expressed in axillary buds, with members of the SOC1 and SVP subfamilies accounting for the majority. Exogenous application of abscisic acid and the strigolactone analog GR24 significantly suppressed the expression of most candidate genes, including NtMADS91. The preliminary overexpression analysis suggested that NtMADS91 may promote axillary bud growth, increasing both the number and length of axillary buds. This study lays a foundation for future dissection of the regulatory mechanisms of the NtMADS-box gene family in axillary bud development and provides promising candidate genes for research related to tobacco axillary bud development.

Nicotiana↗
PubMed2003

The Medicago species A2-type cyclin is auxin regulated and involved in meristem formation but dispensable for endoreduplication-associated developmental programs.

Phytohormones as well as temporal and spatial regulation of the cell cycle play a key role in plant development. Here, we investigated the function and regulation of an alfalfa (Medicago sativa) A2-type cyclin in three distinct root developmental programs: in primary and secondary root development, nodule development, and nematode-elicited gall formation. Using transgenic plants carrying the Medsa;cycA2;2 promoter-beta-glucuronidase gene fusion, in combination with other techniques, cycA2;2 expression was localized in meristems and proliferating cells in the lateral root and nodule primordia. Rapid induction of cycA2;2 by Nod factors demonstrated that this gene is implicated in cell cycle activation of differentiated cells developing to nodule primordia. Surprisingly, cycA2;2 was repressed in the endoreduplicating, division-arrested cells both during nodule development and formation of giant cells in nematode-induced galls, indicating that CycA2;2 was dispensable for S-phase in endoreduplication cycles. Overexpression of cycA2;2 in transgenic plants corresponded to wild type protein levels and had no apparent phenotype. In contrast, antisense expression of cycA2;2 halted regeneration of somatic embryos, suggesting a role for CycA2;2 in the formation or activity of apical meristems. Expression of cycA2;2 was up-regulated by auxins, as expected from the presence of auxin response elements in the promoter. Moreover, auxin also affected the spatial expression pattern of this cyclin by shifting the cycA2;2 expression from the phloem to the xylem poles.

Animals↗
PubMed2005

Mechanisms and function of flower and inflorescence reversion.

Flower and inflorescence reversion involve a switch from floral development back to vegetative development, thus rendering flowering a phase in an ongoing growth pattern rather than a terminal act of the meristem. Although it can be considered an unusual event, reversion raises questions about the nature and function of flowering. It is linked to environmental conditions and is most often a response to conditions opposite to those that induce flowering. Research on molecular genetic mechanisms underlying plant development over the last 15 years has pinpointed some of the key genes involved in the transition to flowering and flower development. Such investigations have also uncovered mutations which reduce floral maintenance or alter the balance between vegetative and floral features of the plant. How this information contributes to an understanding of floral reversion is assessed here. One issue that arises is whether floral commitment (defined as the ability to continue flowering when inductive conditions no longer exist) is a developmental switch affecting the whole plant or is a mechanism which assigns autonomy to individual meristems. A related question is whether floral or vegetative development is the underlying default pathway of the plant. This review begins by considering how studies of flowering in Arabidopsis thaliana have aided understanding of mechanisms of floral maintenance. Arabidopsis has not been found to revert to leaf production in any of the conditions or genetic backgrounds analysed to date. A clear-cut reversion to leaf production has, however, been described in Impatiens balsamina. It is proposed that a single gene controls whether Impatiens reverts or can maintain flowering when inductive conditions are removed, and it is inferred that this gene functions to control the synthesis or transport of a leaf-generated signal. But it is also argued that the susceptibility of Impatiens to reversion is a consequence of the meristem-based mechanisms controlling development of the flower in this species. Thus, in Impatiens, a leaf-derived signal is critical for completion of flowering and can be considered to be the basis of a plant-wide floral commitment that is achieved without accompanying meristem autonomy. The evidence, derived from in vitro and other studies, that similar mechanisms operate in other species is assessed. It is concluded that most species (including Arabidopsis) are less prone to reversion because signals from the leaf are less ephemeral, and the pathways driving flower development have a high level of redundancy that generates meristem autonomy even when leaf-derived signals are weak. This gives stability to the flowering process, even where its initiation is dependent on environmental cues. On this interpretation, Impatiens reversion appears as an anomaly resulting from an unusual combination of leaf signalling and meristem regulation. Nevertheless, it is shown that the ability to revert can serve a function in the life history strategy (perenniality) or reproductive habit (pseudovivipary) of many plants. In these instances reversion has been assimilated into regular plant development and plays a crucial role there.

Environment↗
PubMed2001

[Reproduction and development in flowering plants].

Why mark the centenary of the independent discovery of double fertilization by Sergius Nawashin (1898) and Léon Guignard (1899), when biology has progressed so much since the beginning of the XXth century? This discovery still constitutes one of the key references in plant biology: double fertilization is unique to flowering plants among all living organisms. This meeting is also the occasion to associate angiosperm fertilization with developmental biology because of the localization of this event in the flower. Very important and significant progress has been made in elucidating flower development during the last ten years. And today it is possible to understand the diversity of floral structure present in the angiosperms in the context of a underlying mechanism of flower development inherited from their common ancestor. This special issue also allows a survey of these two broad scientific fields, plant reproduction and plant development (flower and embryo). It might also attract new, talented young scientists.

Botany↗
PubMed2005

Suppression of heterotrimeric G-protein beta-subunit affects anther shape, pollen development and inflorescence architecture in tobacco.

The role of the heterotrimeric G-protein beta-subunit in plant development was studied in transgenic tobacco (Nicotiana tabacum L.) plants with reduced beta-subunit levels due to the antisense expression of the beta-subunit mRNA. The antisense plants had aberrant anther shape and produced non-germinating pollen. The anthers were sporadically transformed to petals, whereas other floral organs were not affected. The pollen grains were smaller than the wild-type pollen and had abnormal cell walls. The architecture of mature antisense plants was altered. The plants had long branched panicles and short stems. These data suggest that the beta-subunit of the plant heterotrimeric G-proteins is involved in the regulation of the reproductive phase of the tobacco life cycle, particularly in stamen development and pollen maturation.

Flowers↗
PubMed2002

GLK gene pairs regulate chloroplast development in diverse plant species.

Chloroplast biogenesis is a complex process that requires close co-ordination between two genomes. Many of the proteins that accumulate in the chloroplast are encoded by the nuclear genome, and the developmental transition from proplastid to chloroplast is regulated by nuclear genes. Here we show that a pair of Golden 2-like (GLK) genes regulates chloroplast development in Arabidopsis. The GLK proteins are members of the GARP superfamily of transcription factors, and phylogenetic analysis demonstrates that the maize, rice and Arabidopsis GLK gene pairs comprise a distinct group within the GARP superfamily. Further phylogenetic analysis suggests that the gene pairs arose through separate duplication events in the monocot and dicot lineages. As in rice, AtGLK1 and AtGLK2 are expressed in partially overlapping domains in photosynthetic tissue. Insertion mutants demonstrate that this expression pattern reflects a degree of functional redundancy as single mutants display normal phenotypes in most photosynthetic tissues. However, double mutants are pale green in all photosynthetic tissues and chloroplasts exhibit a reduction in granal thylakoids. Products of several genes involved in light harvesting also accumulate at reduced levels in double mutant chloroplasts. GLK genes therefore regulate chloroplast development in diverse plant species.

Amino Acid Sequence↗
PubMed2005

The Arabidopsis AtRaptor genes are essential for post-embryonic plant growth.

BACKGROUND: Flowering plant development is wholly reliant on growth from meristems, which contain totipotent cells that give rise to all post-embryonic organs in the plant. Plants are uniquely able to alter their development throughout their lifespan through the generation of new organs in response to external signals. To identify genes that regulate meristem-based growth, we considered homologues of Raptor proteins, which regulate cell growth in response to nutrients in yeast and metazoans as part of a signaling complex with the target of rapamycin (TOR) kinase. RESULTS: We identified AtRaptor1A and AtRaptor1B, two loci predicted to encode Raptor proteins in Arabidopsis. Disruption of AtRaptor1B yields plants with a wide range of developmental defects: roots are thick and grow slowly, leaf initiation and bolting are delayed and the shoot inflorescence shows reduced apical dominance. AtRaptor1A AtRaptor1B double mutants show normal embryonic development but are unable to maintain post-embryonic meristem-driven growth. AtRaptor transcripts accumulate in dividing and expanding cells and tissues. CONCLUSION: The data implicate the TOR signaling pathway, a major regulator of cell growth in yeast and metazoans, in the maintenance of growth from the shoot apical meristem in plants. These results provide insights into the ways in which TOR/Raptor signaling has been adapted to regulate plant growth and development, and indicate that in plants, as in other eukaryotes, there is some Raptor-independent TOR activity.

Arabidopsis↗
PubMed1998

The Tangled1 gene is required for spatial control of cytoskeletal arrays associated with cell division during maize leaf development.

The cytoskeleton plays a major role in the spatial regulation of plant cell division and morphogenesis. Arrays of microtubules and actin filaments present in the cell cortex during prophase mark sites to which phragmoplasts and associated cell plates are guided during cytokinesis. During interphase, cortical microtubules are believed to influence the orientation of cell expansion by guiding the pattern in which cell wall material is laid down. Little is known about the mechanisms that regulate these cytoskeleton-dependent processes critical for plant development. Previous work showed that the Tangled1 (Tan1) gene of maize is required for spatial regulation of cytokinesis during maize leaf development but not for leaf morphogenesis. Here, we examine the cytoskeletal arrays associated with cell division and morphogenesis during the development of tan1 and wild-type leaves. Our analysis leads to the conclusion that Tan1 is required both for the positioning of cytoskeletal arrays that establish planes of cell division during prophase and for spatial guidance of expanding phragmoplasts toward preestablished cortical division sites during cytokinesis. Observations on the organization of interphase cortical microtubules suggest that regional influences may play a role in coordinating cell expansion patterns among groups of cells during leaf morphogenesis.

Actins↗