Plant development and stress responses are regulated by complex signalling networks that mediate specific and dynamic plant responses upon activation by various types of exogenous and endogenous ...signal. In this review, we focus on the latest published work on jasmonate (JA) signalling components and new regulatory nodes in the transcriptional network that regulates a number of diverse plant responses to developmental and environmental cues. Not surprisingly, the majority of the key revelations in the field have been made in Arabidopsis thaliana. However, for comparative reasons, we integrate information on Arabidopsis with recent reports for other plant species (when available). Recent findings on the regulation of plant responses to pathogens by JAs, as well as new evidence implicating JAs in the regulation of senescence, suggest a common mechanism of JA action in these responses via distinct groups of transcription factors. Moreover, a significant increase in the amount of evidence has allowed placing of specific mitogen-activated protein kinases (MAPKs) as crucial regulatory nodes in the defence signalling network. In addition, we report on new physiological scenarios for JA signalling, such as organogenesis of nitrogen-fixing nodules and anticancer therapy.
Phytohormones regulate plant growth from cell division to organ development. Jasmonates (JAs) are signaling molecules that have been implicated in stress-induced responses. However, they have also ...been shown to inhibit plant growth, but the mechanisms are not well understood. The effects of methyl jasmonate (MeJA) on leaf growth regulation were investigated in Arabidopsis (Arabidopsis thaliana) mutants altered in JA synthesis and perception, allene oxide synthase and coil-16B (for coronatine insensitive1), respectively. We show that MeJA inhibits leaf growth through the JA receptor COI1 by reducing both cell number and size. Further investigations using flow cytometry analyses allowed us to evaluate ploidy levels and to monitor cell cycle progression in leaves and cotyledons of Arabidopsis and/or Nicotiana benthamiana at different stages of development. Additionally, a novel global transcription profiling analysis involving continuous treatment with MeJA was carried out to identify the molecular players whose expression is regulated during leaf development by this hormone and COI1. The results of these studies revealed that MeJA delays the switch from the mitotic cell cycle to the endoreduplication cycle, which accompanies cell expansion, in a COI1 -dependent manner and inhibits the mitotic cycle itself, arresting cells in G1 phase prior to the S-phase transition. Significantly, we show that MeJA activates critical regulators of endoreduplication and affects the expression of key determinants of DNA replication. Our discoveries also suggest that MeJA may contribute to the maintenance of a cellular "stand-by mode" by keeping the expression of ribosomal genes at an elevated level. Finally, we propose a novel model for MeJA-regulated COI1 -dependent leaf growth inhibition.
Summary
PtdIns‐4,5‐bisphosphate is a lipid messenger of eukaryotic cells that plays a critical role in processes such as cytoskeleton organization, intracellular vesicular trafficking, secretion, ...cell motility, regulation of ion channels and nuclear signalling pathways. The enzymes responsible for the synthesis of PtdIns(4,5)P2 are phosphatidylinositol phosphate kinases (PIPKs). The moss Physcomitrella patens contains two PIPKs, PpPIPK1 and PpPIPK2. To study their physiological role, both genes were disrupted by targeted homologous recombination and as a result mutant plants with lower PtdIns(4,5)P2 levels were obtained. A strong phenotype for pipk1, but not for pipk2 single knockout lines, was obtained. The pipk1 knockout lines were impaired in rhizoid and caulonemal cell elongation, whereas pipk1‐2 double knockout lines showed dramatic defects in protonemal and gametophore morphology manifested by the absence of rapidly elongating caulonemal cells in the protonemal tissue, leafy gametophores with very short rhizoids, and loss of sporophyte production. pipk1 complemented by overexpression of PpPIPK1 fully restored the wild‐type phenotype whereas overexpression of the inactive PpPIPK1E885A did not. Overexpression of PpPIPK2 in the pipk1‐2 double knockout did not restore the wild‐type phenotype demonstrating that PpPIPK1 and PpPIPK2 are not functionally redundant. In vivo imaging of the cytoskeleton network revealed that the shortened caulonemal cells in the pipk1 mutants was the result of the absence of the apicobasal gradient of cortical F‐actin cables normally observed in wild‐type caulonemal cells. Our data indicate that both PpPIPKs play a crucial role in the development of the moss P. patens, and particularly in the regulation of tip growth.
The vegetative phenotype of the auxin-resistant diageotropica (dgt) mutant of tomato (Lycopersicon esculentum Mill.) includes reduced gravitropic response, shortened internodes, lack of lateral ...roots, and retarded vascular development. Here, we report that early fruit development is also dramatically altered by the single-gene dgt lesion. Fruit weight, fruit set, and numbers of locules and seeds are reduced in dgt. In addition, time to flowering and time from anthesis to the onset of fruit ripening are increased by the dgt lesion, whereas ripening is normal. The dgt mutation appears to affect only the early stages of fruit development, irrespective of allele or genetic background. Expression of members of the LeACS (1-aminocyclopropane-1-carboxylic acid synthase, a key regulatory enzyme of ethylene biosynthesis) and LeIAA (Aux/IAA, auxin-responsive) gene families were quantified via real-time reverse transcriptase-polymerase chain reaction in both dgt and wild-type fruits, providing the first analysis of Aux/IAA gene expression in fruit. The dgt lesion affects the expression of only certain members of both the LeACS and LeIAA multigene families. Different subsets of LeIAA gene family members are affected by the dgt mutation in fruits and hypocotyls, indicating that the DGT gene product functions in a developmentally specific manner. The differential expression of subsets of LeIAA and LeACS gene family members as well as the alterations in dgt fruit morphology and growth suggest that the early stages of fruit development in tomato are regulated, at least in part, by auxin- and ethylene-mediated gene expression.
The plant hormone jasmonate inhibits leaf growth by delaying the switch from the mitotic cell cycle to the endoreduplication cycle and maintains the cell in a stand-by mode but ready-to-go after the ...stress.
Phytohormones regulate plant growth from cell division to organ development. Jasmonates (
JAs
) are signaling molecules that have been implicated in stress-induced responses. However, they have also been shown to inhibit plant growth, but the mechanisms are not well understood. The effects of methyl jasmonate (
MeJA
) on leaf growth regulation were investigated in Arabidopsis (
Arabidopsis thaliana
) mutants altered in
JA
synthesis and perception,
allene oxide synthase
and
coi1
-16B (for
coronatine insensitive1
), respectively. We show that
MeJA
inhibits leaf growth through the
JA
receptor
COI1
by reducing both cell number and size. Further investigations using flow cytometry analyses allowed us to evaluate ploidy levels and to monitor cell cycle progression in leaves and cotyledons of Arabidopsis and/or
Nicotiana benthamiana
at different stages of development. Additionally, a novel global transcription profiling analysis involving continuous treatment with
MeJA
was carried out to identify the molecular players whose expression is regulated during leaf development by this hormone and
COI1
. The results of these studies revealed that
MeJA
delays the switch from the mitotic cell cycle to the endoreduplication cycle, which accompanies cell expansion, in a
COI1
-dependent manner and inhibits the mitotic cycle itself, arresting cells in G1 phase prior to the S-phase transition. Significantly, we show that
MeJA
activates critical regulators of endoreduplication and affects the expression of key determinants of DNA replication. Our discoveries also suggest that
MeJA
may contribute to the maintenance of a cellular “stand-by mode” by keeping the expression of ribosomal genes at an elevated level. Finally, we propose a novel model for
MeJA
-regulated
COI1
-dependent leaf growth inhibition.
The vegetative phenotype of the auxin-resistant
diageotropica
(
dgt
) mutant of tomato (
Lycopersicon esculentum
Mill.) includes reduced gravitropic response, shortened internodes, lack of lateral ...roots, and retarded vascular development. Here, we report that early fruit development is also dramatically altered by the single-gene
dgt
lesion. Fruit weight, fruit set, and numbers of locules and seeds are reduced in
dgt
. In addition, time to flowering and time from anthesis to the onset of fruit ripening are increased by the
dgt
lesion, whereas ripening is normal. The
dgt
mutation appears to affect only the early stages of fruit development, irrespective of allele or genetic background. Expression of members of the
LeACS
(1-aminocyclopropane-1-carboxylic acid synthase, a key regulatory enzyme of ethylene biosynthesis) and
LeIAA
(
Aux/IAA
, auxin-responsive) gene families were quantified via real-time reverse transcriptase-polymerase chain reaction in both
dgt
and wild-type fruits, providing the first analysis of
Aux/IAA
gene expression in fruit. The
dgt
lesion affects the expression of only certain members of both the
LeACS
and
LeIAA
multigene families. Different subsets of
LeIAA
gene family members are affected by the
dgt
mutation in fruits and hypocotyls, indicating that the DGT gene product functions in a developmentally specific manner. The differential expression of subsets of
LeIAA
and
LeACS
gene family members as well as the alterations in
dgt
fruit morphology and growth suggest that the early stages of fruit development in tomato are regulated, at least in part, by auxin- and ethylene-mediated gene expression.
Plant hormones regulate progression through the different phases of plant development in response to endogenous and environmental cues. Gene expression studies, as well as genetic and molecular ...analysis of mutants with altered hormonal responses, are two common approaches to elucidate hormone response pathways. This dissertation compares ovary and fruit development in both wild-type tomatoes and the diageotropica (dgt) auxin-resistant mutant, and analyzes the interactions between the plant hormones auxin and ethylene that regulate gravitropism and lateral root formation. Fruit development is dramatically affected by the dgt mutation; resulting in reduced fruit weight, lower numbers of locules and seeds, delayed time to flowering, and extended developmental time between anthesis and the onset of fruit ripening. Relative quantification of expression patterns for genes involved in ethylene biosynthesis (the ACC synthase, LeACS, gene family) and auxin responsiveness (the Aux/IAA, LeIAA, family of auxin responsive genes) was used to provide insights into the involvement of auxin and ethylene in the regulation of fruit development in tomato. Only a subset of the LeACS and LeIAA gene family members are affected by the dgt lesion, specifically at early stages of fruit development. Changes in cell number and size during ovary and early fruit development were monitored by microscopic analysis. The difference in final fruit size between dgt and wild-type tomatoes correlates with differences in cell number and size that are established pre-anthesis. Differences in the percentage of nuclei present at 2C and 4C at pre-anthesis and anthesis in dgt versus wild-type ovaries suggests a possible delay in cell cycle progression in the dgt ovaries. The expression of four LeIAA genes exhibited differential developmental specificity in developing fruits, as well as differential regulation by the DGT gene product. Interactions between auxin and ethylene were further investigated by analyzing gravitropic responsiveness and lateral root formation in dgt and ethylene-resistant Never-ripe ( Nr) tomato seedlings, F1, and backcross populations. The Nr lesion has no effect on the reduced gravitropic response of dgt plants, while the dgt mutant is partially dominant with respect to gravitropism. In regard to lateral root formation, dgt is completely recessive and seems to be epistatic to Nr.
Objective
To study ophthalmological manifestations in a well-characterized primary antiphospholipid syndrome (PAPS) cohort (APS-Rio) and compare them with a healthy control group.
Methods
We examined ...PAPS patients and controls with an extensive ophthalmological evaluation, which included anamnesis, visual acuity, slit-lamp biomicroscopy, binocular indirect ophthalmoscopy, and retinography of the anterior and posterior segments of the eye. PAPS group also underwent angiography exam and optical coherence tomography using spectral domain technology (SD-OCT).
Results
98 PAPS patients and 102 controls were included. The most common symptom in PAPS was amaurosis fugax (34.7% vs. 6.9%; p = .001). In the multivariate analyses, Raynaud’s phenomenon was associated with amaurosis fugax (OR 3.71, CI:1.33–10.32; p = .012), and livedo correlated with hemianopia (OR 6.96, CI:1.11–43.72, p = .038) and diplopia (OR 3.49, CI:1.02–11.53, p = .047). After ophthalmological evaluation, 84 PAPS patients had ocular involvement (1.0% glaucoma, 94.0% posterior findings, 62.7% anterior findings, and 56.6% both posterior and anterior findings). Vascular tortuosity was more frequent in the PAPS group (63.2% vs. 42.2%; p = .002), as well as peripheral tortuosity (29.6% vs. 7.8%; p < .001). After excluding patients with atherosclerotic risk factors, peripheral vascular tortuosity was still statistically associated with PAPS (35.0 vs. 7.8%, p < .001). Triple positivity was more frequent in PAPS patients with peripheral vascular tortuosity than in those without this ocular finding (34.5% vs. 15.9%, p = .041).
Conclusion
Vasomotor phenomena are importantly related to ocular symptoms in PAPS. Vascular tortuosity was a frequent finding in PAPS patients. Peripheral vascular tortuosity was associated with triple positivity and might be a biomarker of ischemic microvascular retinopathy due to PAPS.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Herein, we studied the occurrence of insect galls from natural vegetation around the Itambé Cave, Altinópolis, SP, Brazil. A sampling effort of 7.5 hours resulted in 41 gall morphotypes on 21 host ...plant species from 14 families. The richest families of host plants in morphotypes were Fabaceae (N = 11), Euphorbiaceae (N = 7), and Malpighiaceae (N = 5). Copaifera langsdorffii Desf. (N = 8), Croton floribundus Spreng. (N = 7), Diplopterys pubipetala (A. Juss.) W.R. Anderson & C.C. Davis (N = 5), and Bauhinia holophylla (Bong.) Steud. (N = 4) were the super host plant species. Among the gall makers obtained, cecidomyiids were reared in 81% of cases and Hemiptera (Diaspididae), Hymenoptera (Eurytomidae), Coleoptera (Apion sp./Apionidae), and Lepidoptera in 4.5% of cases, each. The parasitoids belong to the Chalcidoidea superfamily (Hymenoptera). One new species of Camptoneuromyiia (Cecidomyiidae) was found in Smilax oblongifolia Pohl ex Griseb. (Smilacaceae) as inquiline and a new species of Lestodiplosis in Diplopterys pubipetala (Malpighiaceae) was a predator. We also present the first register of Bauhinia holophylla as host plants of Cecidomyiidae, and we expand the occurrence of Rochadiplosis tibouchinae Tavares and Couridiplosis vena to São Paulo State. The results of this paper are a continuation of the description of gall morphotypes from the vegetation in Northeastern São Paulo State, and they also increase knowledge about the diversity of host plant and gall-maker associations in the Neotropical region.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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