RESUMO
The inheritance of chloroplast DNA (cpDNA) in Leucadendron species was studied by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. A total of 100 progeny from five interspecific crosses involving seven parental species were tested, and all progeny exhibited the cpDNA restriction fragment pattern of the female parent, indicating that cpDNA in Leucadendron is maternally inherited. PCR-RFLP was also employed to study cpDNA variation among 21 Leucadendron species. Parsimony analysis using a heuristic search resulted in a phylogenetic tree that showed limited agreement to the taxonomic classification of Leucadendron species, based on morphological characteristics. The incongruence between cpDNA phylogenetic and taxonomic groupings in Leucadendron may be due to reticulate evolution involving a combination of hybridization and introgression, convergent evolution and/or lineage sorting at the interspecific, intersubsectional and intersectional levels.
Assuntos
DNA de Cloroplastos/genética , Variação Genética , Padrões de Herança/genética , Filogenia , Proteaceae/genética , Cruzamentos Genéticos , Primers do DNA , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , Proteaceae/classificação , Austrália OcidentalRESUMO
Recent evidence suggests that in plants, as in vertebrates, natriuretic peptides (NPs) regulate homeostasis. In this study noninvasive ion-selective vibrating microelectrodes were used to measure net fluxes of K+, Na+, and H+ in Zea mays root conductive tissue. Immunoreactant plant natriuretic peptides (irPNP) cause immediate net H+ influx and delayed net K+ and Na+ uptake. Delayed net K+ influx was also observed in response to 8-Br-cGMP, however, not accompanied by significant changes in net H+ fluxes. Furthermore, 8-Br-cGMP does not stimulate the plasma membrane H+-ATPase implying that cGMP directly affects cation channels. The data are consistent with NP and cGMP-dependent stimulation of nonselective cation channels with P(K) > P(Na) and point to a complex role for NPs in plant homeostasis.
Assuntos
GMP Cíclico/análogos & derivados , Hidrogênio/metabolismo , Peptídeos/metabolismo , Proteínas de Plantas/metabolismo , Potássio/metabolismo , Sódio/metabolismo , Tionucleotídeos/metabolismo , Zea mays/fisiologia , Marcadores de Afinidade , Animais , Fator Natriurético Atrial/metabolismo , Fator Natriurético Atrial/farmacologia , Cátions Monovalentes , GMP Cíclico/metabolismo , GMP Cíclico/farmacologia , Eletroforese em Gel de Poliacrilamida , Immunoblotting , Modelos Biológicos , Peptídeos/química , Peptídeos/farmacologia , Proteínas de Plantas/química , Proteínas de Plantas/farmacologia , Raízes de Plantas/metabolismo , Raízes de Plantas/fisiologia , Ratos , Tionucleotídeos/farmacologia , Zea mays/química , Zea mays/metabolismoRESUMO
Immunological evidence suggest that plants contain natriuretic peptides (NPs) and furthermore (3-[I]iodotyrosol) rat atrial NP (rANP) binds specifically to plant membranes. rANP and immunoaffinity-purified plant NP analogues also promote concentration-dependent stomatal opening. Here we report that kinetin, a synthetic cytokinin, and rANP induce stomatal opening in Tradescantia albiflora and that the effect of rANP is critically dependent on the secondary structure of the peptide hormone. The native circular molecule is active, whereas the linearized molecule shows no biological activity. Furthermore, kinetin- and rANP-induced stomatal opening is reversibly inhibited by two inhibitors of guanylate cyclase, LY 83583 and methylene blue. Stomatal opening is also induced in a concentration-dependent manner by the cell-permeant cyclic guanosine-3',5'-monophosphate (cGMP) analogue 8-Br-cGMP, and this effect is prevented by the stomatal closure promoting plant hormone abscisic acid (ABA). We conclude that in guard cells kinetin and rANP pathways operate via guanylate cyclase upregulation, and we propose that ABA-induced closure is not cGMP-dependent.
Assuntos
Adenina/análogos & derivados , GMP Cíclico/fisiologia , Natriuréticos/fisiologia , Peptídeos/fisiologia , Folhas de Planta/metabolismo , Proteínas de Plantas/fisiologia , Adenina/fisiologia , Sequência de Aminoácidos , Cinetina , Dados de Sequência Molecular , Natriuréticos/química , Peptídeos/química , Folhas de Planta/citologia , Folhas de Planta/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacosRESUMO
It has recently been demonstrated that antibodies against atrial natriuretic peptides (ANP) recognise analogues in plants and that rat ANP binds specifically to isolated plant membranes and promotes stomatal guard cell opening in a concentration dependent manner. Here we report the isolation and immunoaffinity purification of plant natriuretic peptide (PNP) from ivy (Hedera helix) with rabbit anti-alpha-ANP (1-28) (human, canine) antiserum. We also demonstrate that immunoaffinity purified plant peptide induces stomatal opening in a concentration dependent manner. This is therefore the first report of an active indigenous peptide hormone in plants. We propose that PNPs are part of a signalling system that has evolved early in evolution and is involved in the regulation of ion transport and transpiration in plants.
