Formamidines interact withDrosophila octopamine receptors,alter the flies' behavior and reduce their learning ability

Summary We have studied the effect of formamidines onDrosophila melanogaster. Low concentrations of formamidines are toxic to adultDrosophila. A mutant with reduced cAMP synthesis displays increased resistance to the toxin. Formamidines also reduce viability ofDrosophila eggs and retard imago eclosion. At sublethal concentrations, formamidines markedly affect the flies' behavior. Upon injection, the compounds increase muscle activity. Upon feeding, formamidines induce motor excitation, reduce phototaxis and impair olfactory learning without affecting the ability to recognize an olfactory cue. In vitro, two formamidines were found to inhibit octopamine-stimulated adenylate cyclase without affecting the basal activity of the enzyme, while a third one was found to stimulate adenylate cyclase; this stimulation was blocked by phentolamine and to a lesser degree by propranolol, thus resembling the effect of octopamine. The binding of [³H]octopamine toDrosophila head membranes was also inhibited. Taken together, our results indicate that formamidines interact with octopaminergic systems inDrosophila, exert both peripheral and central effects in the fly, and could be used to dissect the roles of octopamine in development and behavior, including behavioral plasticity. The results also suggest that formamidines could be used to select mutants in aminergic transmission and in the cAMP cascade.Abbreviations CDMF chlordimeform - DMPF N,N-dimethyl-N2-(2,4-dimethylphenyl) formamidine     

Fine structure and primary sensory projections of sensilla located in the sacculus of the antenna of Drosophila melanogaster

Sensilla lining the inner walls of the sacculus on the third antennal segment of Drosophila melanogaster were studied by light and transmission electron microscopy. The sacculus consists of three chambers: I, II and III. Inside each chamber morphologically distinct groups of sensilla having inflexible sockets were observed. Chamber I contains no-pore sensilla basiconica (np-SB). The lumen of all np-SB are innervated by two neurons, both resembling hygroreceptors. However, a few np-SB contain one additional neuron, presumed to be thermoreceptive. Chamber II houses no-pore sensilla coeloconica (np-SC). All np-SC are innervated by three neurons. The outer dendritic segments of two of these neurons fit tightly to the wall of the lumen and resemble hygroreceptor neurons. A third, more electron-dense sensory neuron, terminates at the base of the sensillum and resembles a thermoreceptor cell. Chamber III of the sacculus is divided into ventral and dorsal compartments, each housing morphologically distinct grooved sensilla (GS). The ventral compartment contains thick GS₁, and the dorsal compartment has slender sensilla GS₂. Ultrastructurally, both GS₁ and GS₂ are doublewalled sensilla with a longitudinal slit-channel system and are innervated by two neurons. The dendritic outer segment of one ofthe two neurons innervates the lumen of the GS and branches. On morphological criteria, we infer this neuron to be olfactory. The other sensory neuron is probably thermoreceptive. Thus, the sacculus in Drosophila has sensilla that are predominantly involved in hygroreception, thermoreception, and olfaction. We have traced the sensory projections of the neurons innervating the sacculus sensilla of chamber III using cobaltous lysine or ethanolic cobalt (II) chloride. The fibres project to the antennal lobes, and at least four glomeruli (VM₃, DA₃ and DL_2-3) are projection areas of sensory neurons from these sensilla. glomerulus DL₂ is a common target for the afferent fibres of the surface sensilla coeloconica and GS, whereas the VM₃, DA₃ and DL₃ glomeruli receive sensory fibres only from the GS.     

Olfactory physiology in the Drosophila maxillary palp requires the visual system gene rdgB

We describe the kinetics of odorant response in the maxillary palp of Drosophila, and show that the rate of recovery from odorant stimulation is affected by mutation of the rdgB (retinal degeneration B) gene. We use immunocytochemistry to confirm that the rdgB gene product is expressed in the maxillary palp. rdgB has recently been shown to encode a protein with Ca²⁺-binding sites and sequence similarity to rat brain phosphatidylinositol transfer protein; it is located near the rhabdomeric membranes in photoreceptor cells, where it has been suggested to play a role in membrane transport. The delay in recovery kinetics that we observe in olfactory tissue may reflect a defect in membrane restoration at the conclusion of the olfactory transduction cascade. The use of common molecules in the physiology of two olfactory organs, and in both visual and olfactory physiology, is discussed.Abbreviations EAG electroantennogram - EPG electropalpogram - ERG electroretinogram - norpA no receptor potential A - PBS phosphate buffered saline - rdgB retinal degeneration B - PI phosphatidylinositol     

Modulation of dihydropyridine‐sensitive calcium channels in drosophila by a cAMP‐mediated pathway

Drosophila has proved to be a valuable system for studying the structure and function of ion channels. However, relatively little is known about the regulation of ion channels, particularly that of Ca²⁺ channels, in Drosophila. Physiological and pharmacological differences between invertebrate and mammalian L‐type Ca²⁺ channels raise questions on the extent of conservation of Ca²⁺ channel modulatory pathways. We have examined the role of cyclic adenosine monophosphate (cAMP) cascade in modulating the dihydropyridine (DHP)‐sensitive Ca²⁺ channels in the larval muscles of Drosophila, using mutations and drugs that disrupt specific steps in this pathway. The L‐type (DHP‐sensitive) Ca²⁺ channel current was increased in the dunce mutants, which have high cAMP concentration owing to cAMP‐specific phosphodiesterase (PDE) disruption. The current was decreased in the rutabaga mutants, where adenylyl cyclase (AC) activity is altered thereby decreasing the cAMP concentration. The dunce effect was mimicked by 8‐Br‐cAMP, a cAMP analog, and IBMX, a PDE inhibitor. The rutabaga effect was rescued by forskolin, an AC activator. H‐89, an inhibitor of protein kinase‐A (PKA), reduced the current and inhibited the effect of 8‐Br‐cAMP. The data suggest modulation of L‐type Ca²⁺ channels of Drosophila via a cAMP‐PKA mediated pathway. While there are differences in L‐type channels, as well as in components of cAMP cascade, between Drosophila and vertebrates, main features of the modulatory pathway have been conserved. The data also raise questions on the likely role of DHP‐sensitive Ca²⁺ channel modulation in synaptic plasticity, and learning and memory, processes disrupted by the dnc and the rut mutations. © 1999 John Wiley & Sons, Inc. J Neurobiol 39: 491–500, 1999     

Fine structure of a sensory organ in the arista of Drosophila melanogaster and some other dipterans

Summary The arista, a characteristic appendage of dipteran antennae, consists of 2 short segments at the base and a long distal shaft. A small sensory ganglion, from which arises the aristal nerve, is located proximally in the shaft. The fine structure of the aristal sensory organ was studied in detail in the fruitfly (Drosophila) and for comparison in the housefly (Musca) and the blowfly (Calliphora). In Drosophila, the aristal sense organ consists of 3 identical sensilla that terminate in the hemolymph space of the aristal shaft, and not in an external cuticular apparatus. Each sensillum comprises 2 bipolar neurons and 2 sheath cells; a third sheath cell envelops the somata of all six neurons of the ganglion. The neurons have long slender dendrites with the usual subdivision into an inner and an outer segment. One of the outer segments is highly lamellated and bears small particles (BOSS-structures) on the outside of its cell membrane; the other outer segment is unbranched and has a small diameter. The fine structure of the first dendrite is strongly reminiscent of thermoreceptors known from the antennae of other insects. These thermoreceptors are often coupled with hygroreceptors; however, we can only speculate whether the second dendrite of the aristal organ also has this function. Our present results argue against mechanoreceptive functions, as formerly postulated. The aristal sense organs in Musca and Calliphora are similar to those in Drosophila, but contain more sensilla (12 in Musca, 18 in Calliphora).     

Activity-dependent induction of facilitation,depression, and post-tetanic potentiation at an insect central synapse

Summary In Manduca sexta larvae, sensory neurons innervating planta hairs on the tips of the prolegs make monosynaptic excitatory connections with motoneurons innervating proleg retractor muscles. Tactile stimulation of the hairs evokes reflex retraction of the proleg. In this study we examined activity-dependent changes in the amplitude of the excitatory postsynaptic potentials (EPSPs) evoked in a proleg motoneuron by stimulation of individual planta hair sensory neurons. Deflection of a planta hair caused a phasic-tonic response in the sensory neuron, with a mean peak instantaneous firing frequency of >300 Hz, and a tonic firing rate of 10–20 Hz. Direct electrical stimulation was used to activate individual sensory neurons to fire at a range of frequencies including those observed during natural stimulation of the hair. At relatively low firing rates (e.g., 1 Hz), EPSP amplitude was stable indefinitely. At higher instantaneous firing frequencies (>10 Hz), EPSPs were initially facilitated, but continuous stimulation led rapidly to synaptic depression. High-frequency activation of a sensory neuron could also produce post-tetanic potentiation, in which EPSP amplitude remained elevated for several min following a stimulus train. Facilitation, depression, and post-tetanic potentiation all appeared to be presynaptic phenomena. These activity-dependent changes in sensory transmission may contribute to the behavioral plasticity of the proleg withdrawal reflex observed in intact insects.Abbreviations ACh acetylcholine - AChE acetylcholine esterase - CNS central nervous system - EPSP excitatory postsynaptic potential - I _h injected hyperpolarizing current - LTP long-term potentiation - PPR principal planta retractor motoneuron - PTP post-tetanic potentiation - R _in input resistance - V _h hyperpolarized potential - V _m membrane potential - VN ventral nerve - VNA anterior branch of the ventral nerve - V _r resting potential.     

CDK inhibitors suppress apoptosis induced by chemicals and by excessive expression of a cell death gene, reaper, in Drosophila cells

The present study was aimed to investigate whether or not cyclin-dependent kinases (CDKs) participate in different cascades leading to apoptosis. We examined the effects of two CDK inhibitors, olomoucine (OLM) and buty-rolactone-I (BL-I), on apoptosis induced in two kinds of Drosophila cell lines. Increases of caspase activity induced by actinomycin D, cycloheximide, H-7 or A23187 in a Drosophila neuronal cell line, ML-DmBG2-c2, and induced by excessive expression of a Drosophila cell death gene, reaper, in Drosophila S2 cells were suppressed by 24-h pretreatment of each CDK inhibitor. Concomitant with the suppression of the caspase activity, fragmentations of cells and DNA, representatives of apoptosis, were also inhibited. These results suggest that CDK(s) participates in progression of apoptosis. However, these effects of the CDK inhibitors were also observed even at lower doses which did not affect cell proliferation. Therefore, it was shown that apoptosis is not always related to cell cycle in Drosophila cells. It was also suggested that the target(s) of the CDK inhibitors locates upstream of caspase in the cascade(s) of apoptosis.     

The whole-body shortening reflex of the medicinal leech: motor pattern,sensory basis,and interneuronal pathways

The leech whole-body shortening reflex consists of a rapid contraction of the body elicited by a mechanical stimulus to the anterior of the animal. We used a variety of reduced preparations — semi-intact, body wall, and isolated nerve cord — to begin to elucidate the neural basis of this reflex in the medicinal leech Hirudo medicinalis. The motor pattern of the reflex involved an activation of excitatory motor neurons innervating dorsal and ventral longitudinal muscles (dorsal excitors and ventral excitors respectively), as well as the L cell, a motor neuron innervating both dorsal and ventral longitudinal muscles. The sensory input for the reflex was provided primarily by the T (touch) and P (pressure) types of identified mechanosensory neuron. The S cell network, a set of electrically-coupled interneurons which makes up a fast conducting pathway in the leech nerve cord, was active during shortening and accounted for the shortest-latency excitation of the L cells. Other, parallel, interneuronal pathways contributed to shortening as well. The whole-body shortening reflex was shown to be distinct from the previously described local shortening behavior of the leech in its sensory threshold, motor pattern, and (at least partially) in its interneuronal basis.Abbreviations conn connective - DE dorsal excitor motor neuron - DI dorsal inhibitor motor neuron - DP dorsal posterior nerve - DP:B1 dorsal posterior nerve branch 1 - DP:B2 dorsal posterior nerve branch 2 - MG midbody ganglion - VE ventral excitor motor neuron - VI ventral inhibitor motor neuron     

Analysis of neural elements in head-mutant Drosophila embryos suggests segmental origin of the optic lobes

We describe the development of 20 sensory organs in the embryonic Drosophila head, which give rise to 7 sensory nerves of the peripheral nervous system (PNS), and 4 ganglia of the stomatogastric nervous system (SNS). Using these neural elements and the optic lobes as well as expression domains of the segment polarity gene engrailed in the wild-type head of Drosophila embryos as markers we examined the phenotype of different mutants which lack various and distinct portions of the embryonic head. In the mutants, distinct neural elements and engrailed expression domains, serving as segmental markers, are deleted. These mutants also affect the optic lobes to various degrees. Our results suggest that the optic lobes are of segmental origin and that they derive from the ocular segment anteriorly adjacent to the antennal segment of the developing head.     

Functional and molecular evolution of olfactory neurons and receptors for aliphatic esters across the Drosophila genus

Insect olfactory receptor (Or) genes are large, rapidly evolving gene families of considerable interest for evolutionary studies. They determine the responses of sensory neurons which mediate critical behaviours and ecological adaptations. We investigated the evolution across the genus Drosophila of a subfamily of Or genes largely responsible for the perception of ecologically relevant aliphatic esters; products of yeast fermentation and fruits. Odour responses were recorded from eight classes of olfactory receptor neurons known to express this Or subfamily in D. melanogaster and from homologous sensilla in seven other species. Despite the fact that these species have diverged over an estimated 40 million years, we find that odour specificity is largely maintained in seven of the eight species. In contrast, we observe extensive changes in most neurons of the outgroup species D. virilis, and in two neurons across the entire genus. Some neurons show small shifts in specificity, whilst some dramatic changes correlate with gene duplication or loss. An olfactory receptor neuron response similarity tree did not match an Or sequence similarity tree, but by aligning Or proteins of likely functional equivalence we identify residues that may be relevant for odour specificity. This will inform future structure–function studies of Drosophila Ors.     

Reduction in the intracellular cAMP level triggers initiation of sexual development in fission yeast

Summary Schizosaccharomyces pombe initiates sexual development in response to nutritional starvation. The level of cAMP inS. pombe cells changed during the transition from exponential growth to stationary phase. It also changed in response to a shift from nitrogen-rich medium to nitrogen-free medium. A decrease of approximately 50% was observed in either case, suggesting thatS. pombe cells contain less cAMP when they initiate sexual development.S. pombe cells that expressed the catalytic domain ofSaccharomyces cerevisiae adenylyl cyclase from theS. pombe adh1 promoter contained 5 times as much cAMP as the wild type and could not initiate mating and meiosis. These observations, together with previous findings that exogenously added cAMP inhibits mating and meiosis and that cells with little cAMP are highly derepressed for sexual development, strongly suggest that cAMP functions as a key regulator of sexual development inS. pombe. Thepde1 gene, which encodes a protein homologous toS. cerevisiae cAMP phosphodiesterase I, was isolated as a multicopy suppressor of the sterility caused by a high cAMP level. Disruption ofpde1 madeS. pombe cells partially sterile and meiosis-deficient, indicating that this cAMP phosphodiesterase plays an important role in balancing the cAMP level in vivo.     

Juvenile hormone stimulation of ornithine decarboxylase activity during vitellogenesis in Drosophila melanogaster

Summary The activity of ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, becomes elevated in intact female Drosophila melanogaster shortly after adult eclosion. This activity reaches a peak at 24 h following eclosion, and then drops to lower levels by 48 h. This pattern is not observed in males, consistent with the hypothesis that polyamine synthesis is involved in ovarian maturation in Drosophila. Abdomens isolated within 2 h of adult eclosion do not display elevated ODC activity or ovarian maturation. However, a 250-ng dose of the juvenile hormone analog methoprene (ZR-515) applied in acetone to these abdomens, recovers ovarian maturation and causes a 5–10 fold increase in enzyme activity over controls treated with acetone alone. The same dose of the inactive precursor methyl farnesoate caused no such increase, whereas a 500-ng dose of the newly discovered natural Drosophila JHB₃ stimulated a four-fold response. The response to methoprene was dose-dependent, showing stimulatory activity at a dose as low as 10 ng. This stimulation by JHA is rapid, occurring between 1 and 3 h following hormone treatment, reminiscent of JH induction of fat body vitellogenin synthesis in Drosophila. Elevated ODC activity appeared to be localized in the adult fat body. During embryogenesis, ODC activity remained undetectable until just prior to hatching, when a large increase was detected. We postulate that JH may, either directly or indirectly, regulate polyamine biosynthesis in vivo, and that this synthesis may be required for the production of macromolecules during Drosophila vitellogenesis or embryogenesis.Abbreviations JH juvenile hormone - JHA juvenile hormone analog - ODC ornithine decarboxylase - SAMDC S-adenosyl-methionine decarboxylase - JHB ₃ juvenile hormone III bisepoxide     

Altered mechanoreceptor response in Drosophila bang-sensitive mutants

Bang-sensitive mutants of Drosophila melano gaster (bas ¹, bss^MW1, eas², tko^25t) display seizure followed by paralysis when subjected to mechanical shock. However, no physiological or biochemical defect has been found to be common to all of these mutants. In order to observe the effects of bang-sensitive mutations upon an identified neuron, and to study the nature of mechanically induced paralysis, we examined the response of a mechanosensory neuron in these mutants. In each single mutant and the double mutant bas ¹ bss^MW1, the frequency of action potentials in response to a bristle displacement was reduced. This is the first demonstration of a physiological defect common to several of the bang-sensitive mutations. Adaptation of spike frequency, cumulative adaptation to repeated stimulation (fatigue) and the time course of recovery from adaptation were also examined. Recovery from adaptation to a conditioning stimulus was examined in two mutants (bas ¹ and bss ^MW1), and initial recovery from adaptation was greater in both mutants. Quantification of receptor potentials was complicated by variability inherent in extracellular recording conditions, but examination of the waveform and range of amplitudes did not indicate clear mutant defects. Therefore the differences observed in the spike response may be due to an alteration of the transfer from receptor potentials to action potential production. DNA sequence analysis of tko and eas has indicated that they encode apparently unrelated biochemical products. Our results suggest that these biochemical lesions lead to a common physiological defect in mechanoreceptors. Although this defect does not provide a straightforward explanation for bang sensitivity, the altered cellular process may lead to bang sensitivity through its action in different parts of the nervous system.Abbreviations APA anterior post-alar - ANP anterior notopleural - bas bang-sensitive - bss bang-senseless - eas easily-shocked tko technical knockout     

Presynaptic effectors contributing to cAMP‐induced synaptic potentiation in Drosophila

cAMP analogs and activation of adenylyl cyclase by forskolin strongly potentiate synaptic transmission at the Drosophila neuromuscular junction. These effects are generally attributed to activation of cAMP‐dependent protein kinase. Recent reports on crustacean and mammalian synapses have implicated other cAMP‐dependent effectors in synaptic potentiation. Drosophila neuromuscular junctions were tested for effects of two known cAMP‐dependent effectors: hyperpolarization‐activated, cyclic nucleotide‐regulated channels (HCNCs) and guanine nucleotide exchange protein activated by cAMP (Epac). Forskolin‐induced enhancement of synaptic transmission was drastically reduced by a blocker of HCNCs, but not completely eliminated. A specific agonist for Epac modestly enhanced synaptic potentials. This agonist also stabilized their amplitudes in the presence of a blocker of HCNCs. The observations implicate HCNCs and Epac in cAMP‐dependent potentiation that does not require cAMP‐dependent protein kinase, indicating that additional previously unexplored factors contribute to synaptic plasticity in Drosophila. Genetic and molecular techniques available for Drosophila can be used to define the underlying molecular basis for cAMP‐dependent synaptic potentiation. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2006     

The influence of segmental compartmentalisation on the development of the larval peripheral nervous system in Drosophila melanogaster

Summary The peripheral nervous system of embryos homozygous for prd, ftz, en and bxd was examined for defects and transformations in the segment-specific pattern of sensilla and peripheral nerves. This analysis permitted me to assign a distinct subset of sensilla to any of the three genetically and morphologically defined compartments s, a and p of each segment. In the wild-type embryonic segments, sensory axons deriving from sensilla of different compartments form a part of the common peripheral nerves. In the composite segments of prd and ftz mutant embryos, subsets of sensilla of two neighbouring segments are combined. Nevertheless, the axons of sensilla of different segmental identity are able to fasciculate and to form afferent nerves, which connect in an apparently normal fashion to the central nervous system. It is concluded that in the Drosophila embryo compartmental and segmental identity of sensory organs has no influence on the trajectories of sensory axons.     

IFT52 plays an essential role in sensory cilia formation and neuronal sensory function in Drosophila

Cilia are microtubule-based, hair-like organelles involved in sensory function or motility, playing critical roles in many physiological processes such as reproduction, organ development, and sensory perception. In insects, cilia are restricted to certain sensory neurons and sperms, being important for chemical and mechanical sensing, and fertility. Although great progress has been made regarding the mechanism of cilia assembly, the formation of insect cilia remains poorly understand, even in the insect model organism Drosophila. Intraflagellar transport (IFT) is a cilia-specific complex that traffics protein cargos bidirectionally along the ciliary axoneme and is essential for most cilia. Here we investigated the role of IFT52, a core component of IFT-B, in cilia/flagellar formation in Drosophila. We show that Drosophila IFT52 is distributed along the sensory neuronal cilia, and is essential for sensory cilia formation. Deletion of Ift52 results in severe defects in cilia-related sensory behaviors. It should be noted that IFT52 is not detected in spermatocyte cilia or sperm flagella of Drosophila. Accordingly, ift52 mutants can produce sperms with normal motility, supporting a dispensable role of IFT in Drosophila sperm flagella formation. Altogether, IFT52 is a conserved protein essential for sensory cilia formation and sensory neuronal function in insects.     

Internal representations of smell in the <Emphasis Type="Italic">Drosophila</Emphasis> brain

Recent advances in sensory neuroscience using Drosophila olfaction as a model system have revealed brain maps representing the external world. Once we understand how the brain’s built-in capability generates the internal olfactory maps, we can then elaborate how the brain computes and makes decision to elicit complex behaviors. Here, we review current progress in mapping Drosophila olfactory circuits and discuss their relationships with innate olfactory behaviors. Hui-Hao lin and Chih-Yung Lin contributed equally to this work.     

Mandibular premotor interneurons of larval Manduca sexta

Simultaneous intracellular recordings were made from interneurons and from closer or opener mandibular motor neurons in the isolated suboesophageal ganglion of the larva of Manduca sexta. This article describes various morphologically and physiologically distinguishable premotor spiking interneurons which make direct excitatory connections with the motor neurons. In addition, two presumptive non-spiking interneurons make excitatory and inhibitory connections respectively with opener motor neurons. Both classes of interneurons receive excitatory and inhibitory sensory inputs from the mouthparts. Their circuitry and functions are discussed.Abbreviations A anterior - AP action potential - CEC circumoesophageal connective - Cl-MN closer motor neuron - EPSP excitatory postsynaptic potential - IN interneuron - IPSP inhibitory postsynaptic potential - MdN mandibular nerve - MN motor neuron - MxN maxillary nerve - O-MN opener motor neuron - PSP postsynaptic potential     

Stimulus-induced translocation of the protein kinase A catalytic subunit to the apical membrane in blowfly salivary glands

Secretion in blowfly (Calliphora vicina) salivary glands is regulated by the neurohormone serotonin (5-HT), which activates the InsP₃/Ca²⁺ pathway and the cAMP/protein kinase A (PKA) pathway in the secretory cells. The latter signaling cascade induces the activation of a vacuolar H⁺-ATPase on the apical membrane. Here, we have determined the distribution of PKA by using antibodies against the PKA regulatory subunit-II (PKA-RII) and the PKA catalytic subunit (PKA-C) of Drosophila. PKA is present in high concentrations within the secretory cells. PKA-RII and PKA-C co-distribute in non-stimulated glands, being enriched in the basal portion of the secretory cells. Exposure to 8-CPT-cAMP or 5-HT induces the translocation of PKA-C to the apical membrane, whereas the PKA-RII distribution remains unchanged. The recruitment of PKA-C to the apical membrane corroborates our hypothesis that vacuolar H⁺-ATPase, which is enriched in this membrane domain, is a target protein for PKA. This work was supported by grants Wa463/9–5 and GRK837 from the Deutsche Forschungsgemeinschaft.     

Phosphodiesterase MoPdeH targets MoMck1 of the conserved mitogen‐activated protein (MAP) kinase signalling pathway to regulate cell wall integrity in rice blast fungus Magnaporthe oryzae

In the rice blast fungus Magnaporthe oryzae, the high‐affinity cyclic adenosine monophosphate (cAMP) phosphodiesterase MoPdeH is important not only for cAMP signalling and pathogenicity, but also for cell wall integrity (CWI) maintenance through an unknown mechanism. By utilizing affinity purification, we found that MoPdeH interacts with MoMck1, one of the components of the mitogen‐activated protein (MAP) kinase cascade that regulates CWI. Overexpression of MoMCK1 suppressed defects in autolysis and pathogenicity of the ΔMopdeH mutant, although partially, suggesting that MoPdeH plays a critical role in CWI maintenance mediated by the MAP kinase pathway. We found that MoMck1 and two other MAP kinase cascade components, MoMkk1 and MoMps1, modulate intracellular cAMP levels by regulating the expression of MoPDEH through a feedback loop. In addition, disruption of MoMKK1 resulted in less aerial hyphal formation, defective asexual development and attenuated pathogenicity. Moreover, MoMkk1 plays a role in the response to osmotic stress via regulation of MoOsm1 phosphorylation levels, whereas endoplasmic reticulum (ER) stress enhances MoMps1 phosphorylation and loss of the MAP kinase cascade component affects the unfolded protein response (UPR) pathway. Taken together, our findings demonstrate that MoPdeH functions upstream of the MoMck1–MoMkk1–MoMps1 MAP kinase pathway to regulate CWI, and that MoPdeH also mediates crosstalk between the cAMP signalling pathway, the osmotic sensing high osmolarity glycerol (HOG) pathway and the dithiothreitol (DTT)‐induced UPR pathway in M. oryzae.