P r e f a c e
Preface to the Special Issue
This Special Issue is dawn from papers originally delivered at the First Asian Invertebrate Immunity Symposium (AIIS), convened in Busan, Korea during February 14–15, 2014. This Special Issue presents six papers that represent contemporary advances in invertebrate immunity. The AIIS was planned to share current scientific information on invertebrate immunity among junior and senior scientists of Korea, China, and Japan, and aims to grow in international recognition. The symposium in Busan attracted over 100 attendees from the three countries. The papers in this issue are selected to highlight advances in invertebrate immunity. In the following paragraphs, we introduce each of the six papers in this issue. Professor Bok Luel Lee, and his colleague J.K. Kim, at Busan National University, present a review of insect-bacteria symbioses. Symbiotic bacteria are typically seen as either obligate symbionts, vertically transmitted mutualistic species that are essential for the life of their host insect, or facultative symbionts, which can be beneficial or deleterious to their hosts. This review describes working models of insect-bacterial symbioses, including the pea aphid, the fruit fly, and the tsetse models; and then provides a detailed treatment of the Riptortus-Burkholderia symbiosis. The genome of a specific Burkholderia strain (RPE64) has been sequenced, enabling use of genetically manipulated Burkholderia symbionts to identify key symbiotic factors, that is, bacterial genes essential for establishing a symbiotic relationship in the host gut. For example, they targeted cell wall biosynthesis by mutating the Burkholderia uppP gene, and found that uppP mutants were able to reach the host midgut, but did not survive. Their results with a single-mutated gene showed that peptidoglycan integrity is required to initiate the normal gut symbiotic relationship within the Riptortus-Burkholderia symbiosis. Their work has tremendous ecological and evolutionary significance, showing that symbiotic factors can be identified and manipulated both to understand symbiotic relationships at the molecular level and to open new technologies for ecological management of insect pests. Cytokines comprise a rather loosely defined category of small proteins secreted by cells. They act in autocrine and paracrine modes to influence cell behaviors. Examples include chemokines and interferons. They are heavily studied in biomedicine, less so in insect immunology. Plasmatocyte spreading peptide, paralytic peptide (PP), and growthblocking peptide are three insect cytokines. Ishii and his colleagues at the University of Tokyo provide a detailed review of available information on PP and its actions in the silkworm, Bombyx mori. They show that PP, as the name suggests, produces paralysis in infected silkworms. PP contributes to immune reactions against pathogenic bacteria, in part by influencing expression of over 100 genes in hemocytes and fat body, including ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY, Vol. 88, No. 1, 1–3 (2015) Published online in Wiley Online Library (wileyonlinelibrary.com). C 2014 Wiley Periodicals, Inc. DOI: 10.1002/arch.21220
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Archives of Insect Biochemistry and Physiology, January 2015
phagocytosis-related genes and genes encoding antimicrobial peptides (AMPs). The significance of their paper lies in understanding of biochemical signals that mediate insect immune reactions to pathogenic infections, specifically appreciating the actions of insect cytokines in humoral and cellular immunity. Among the insect humoral immune reactions to bacterial infections, insect produce AMPs. These are relatively small proteins, typically under 100 amino acids in length and they directly interact with bacterial cells, causing loss of membrane integrity, disrupting cell wall biosynthesis, and interfering with cellular signaling pathways. While insects elaborate many AMPs, cecropin, first discovered in pupae of the cecropia moth, Hyalophora cecropia, may be the most widely known one. Many cecropin-like peptides are known, including mammalian cecropin, all of which kill some Gram-negative bacteria. In this issue, Yangmee Kim’s group in Konkuk University reports that cecropins exert strong antimicrobial activity against two species of multidrug resistant bacteria, as may be expected of an AMP. Cecropins also exert anti-inflammatory activity in mammalian cells, including suppression of cytokine release, and blocked intracellular signaling via several pathways. Aside from potentials in biomedical research, cecropins may mediate inflammatory reactions in insects. This finding brightly illuminates an interesting corridor of research into insect inflammatory reactions to challenge. Zhang and his colleagues investigated a prophenoloxidase (PPO) from the saturnid moth, Antheraea pernyi. The authors cloned the A. pernyi gene and expressed it in competent bacterial cells and used the recombinant PPO for standard characterization, including pH and temperature optima. The recombinant enzyme was stimulated by microbial challenge and killed bacteria in radial diffusion assays. Injecting the enzyme into larvae induced transcription of the A. pernyi gene encoding cecropin. Thermolysin is a bacterial metallopeptidase, one of a large number of bacterial proteases that lethally disrupt normal physiology. In larvae of the greater wax moth, Galleria mellonella, for example, thermolysin injections led to deadly activation of plasma PPO. In this Special Issue, Ling and his colleagues report on the influence of thermolysin on silkworms, B. mori. They found thermolysin injections kill experimental larvae, which could not stop bleeding due to damage to the coagulation system. The protease acts in the plasma, because it did not damage Drosophila S2 cells, an established cell line, and it cleaved plasma proteins, including prophenoloxidase, serpin-2, and βGRP-2. Although it does not cleave all insect plasma proteins, thermolysin also processed mammalian plasma proteins. The most valuable advance in this work is showing that thermolysin operates within a physiological context, within plasma on circulating proteins. We infer that thermolysin is a potent element of bacterial pathogenesis. Autophagy, first discovered in the 1960s, is an evolutionarily conserved process that occurs in all eukaryotic cells. It is involved in fundamental processes in development and host defense. Autophagy (from the term autophagocytosis, for “self” and “eat”) is the basic mechanism for intracellular breakdown of cellular components, either to clear out unusable cell components or promote survival during times of energy emergencies. The process involves forming an autophagosome to isolate targets components and fusion with a lysosome for final degradation. In insects autophagy operates during metamorphosis and in host defense. Autophagy is controlled by autophagy-related (Atg) proteins encoded by ATG genes, known from many organisms, including insects. There are several ATG genes, designated as ATG1, ATG2, and so on. Tindwa et al., in Professor Yeon-Soo Han’s laboratory, report on two autophagy genes, ATG3 and ATG5 in the beetle, Tenebrio molitor. They report the complete sequences of both genes, and show that these genes are expressed throughout development in most tissues, particularly fat body and hemocytes. Archives of Insect Biochemistry and Physiology
Preface
r
3
Their key finding is that silencing these two genes by dsRNA treatments reduced survival of the beetle larvae challenged with the intracellular pathogen, Listeria monocytogenes. The significance of this work is the broadening of our appreciation of insect immune reactions to intracellular pathogens. We hope the papers in this Special Issue are of interest to a wide readership. The AIIS was planned to be held at Korea, China, or Japan in a rotating manner every other year following this groundbreaking symposium in 2014. The upcoming symposium is scheduled in China during 2016. We look forward to seeing you there. Guest Editors: Bok Luel Lee Busan National University, Busan, Korea Shun-Ichiro Kawabata Kyushu University, Fukuoka, Japan Chengshu Wang CAS, Shanghai Institutes, Biological Sciences, China Coordinating Editor: Yonggyun Kim Andong National University, Andong, Korea
Archives of Insect Biochemistry and Physiology
Preface to the Special Issue
This Special Issue is dawn from papers originally delivered at the First Asian Invertebrate Immunity Symposium (AIIS), convened in Busan, Korea during February 14–15, 2014. This Special Issue presents six papers that represent contemporary advances in invertebrate immunity. The AIIS was planned to share current scientific information on invertebrate immunity among junior and senior scientists of Korea, China, and Japan, and aims to grow in international recognition. The symposium in Busan attracted over 100 attendees from the three countries. The papers in this issue are selected to highlight advances in invertebrate immunity. In the following paragraphs, we introduce each of the six papers in this issue. Professor Bok Luel Lee, and his colleague J.K. Kim, at Busan National University, present a review of insect-bacteria symbioses. Symbiotic bacteria are typically seen as either obligate symbionts, vertically transmitted mutualistic species that are essential for the life of their host insect, or facultative symbionts, which can be beneficial or deleterious to their hosts. This review describes working models of insect-bacterial symbioses, including the pea aphid, the fruit fly, and the tsetse models; and then provides a detailed treatment of the Riptortus-Burkholderia symbiosis. The genome of a specific Burkholderia strain (RPE64) has been sequenced, enabling use of genetically manipulated Burkholderia symbionts to identify key symbiotic factors, that is, bacterial genes essential for establishing a symbiotic relationship in the host gut. For example, they targeted cell wall biosynthesis by mutating the Burkholderia uppP gene, and found that uppP mutants were able to reach the host midgut, but did not survive. Their results with a single-mutated gene showed that peptidoglycan integrity is required to initiate the normal gut symbiotic relationship within the Riptortus-Burkholderia symbiosis. Their work has tremendous ecological and evolutionary significance, showing that symbiotic factors can be identified and manipulated both to understand symbiotic relationships at the molecular level and to open new technologies for ecological management of insect pests. Cytokines comprise a rather loosely defined category of small proteins secreted by cells. They act in autocrine and paracrine modes to influence cell behaviors. Examples include chemokines and interferons. They are heavily studied in biomedicine, less so in insect immunology. Plasmatocyte spreading peptide, paralytic peptide (PP), and growthblocking peptide are three insect cytokines. Ishii and his colleagues at the University of Tokyo provide a detailed review of available information on PP and its actions in the silkworm, Bombyx mori. They show that PP, as the name suggests, produces paralysis in infected silkworms. PP contributes to immune reactions against pathogenic bacteria, in part by influencing expression of over 100 genes in hemocytes and fat body, including ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY, Vol. 88, No. 1, 1–3 (2015) Published online in Wiley Online Library (wileyonlinelibrary.com). C 2014 Wiley Periodicals, Inc. DOI: 10.1002/arch.21220
2
r
Archives of Insect Biochemistry and Physiology, January 2015
phagocytosis-related genes and genes encoding antimicrobial peptides (AMPs). The significance of their paper lies in understanding of biochemical signals that mediate insect immune reactions to pathogenic infections, specifically appreciating the actions of insect cytokines in humoral and cellular immunity. Among the insect humoral immune reactions to bacterial infections, insect produce AMPs. These are relatively small proteins, typically under 100 amino acids in length and they directly interact with bacterial cells, causing loss of membrane integrity, disrupting cell wall biosynthesis, and interfering with cellular signaling pathways. While insects elaborate many AMPs, cecropin, first discovered in pupae of the cecropia moth, Hyalophora cecropia, may be the most widely known one. Many cecropin-like peptides are known, including mammalian cecropin, all of which kill some Gram-negative bacteria. In this issue, Yangmee Kim’s group in Konkuk University reports that cecropins exert strong antimicrobial activity against two species of multidrug resistant bacteria, as may be expected of an AMP. Cecropins also exert anti-inflammatory activity in mammalian cells, including suppression of cytokine release, and blocked intracellular signaling via several pathways. Aside from potentials in biomedical research, cecropins may mediate inflammatory reactions in insects. This finding brightly illuminates an interesting corridor of research into insect inflammatory reactions to challenge. Zhang and his colleagues investigated a prophenoloxidase (PPO) from the saturnid moth, Antheraea pernyi. The authors cloned the A. pernyi gene and expressed it in competent bacterial cells and used the recombinant PPO for standard characterization, including pH and temperature optima. The recombinant enzyme was stimulated by microbial challenge and killed bacteria in radial diffusion assays. Injecting the enzyme into larvae induced transcription of the A. pernyi gene encoding cecropin. Thermolysin is a bacterial metallopeptidase, one of a large number of bacterial proteases that lethally disrupt normal physiology. In larvae of the greater wax moth, Galleria mellonella, for example, thermolysin injections led to deadly activation of plasma PPO. In this Special Issue, Ling and his colleagues report on the influence of thermolysin on silkworms, B. mori. They found thermolysin injections kill experimental larvae, which could not stop bleeding due to damage to the coagulation system. The protease acts in the plasma, because it did not damage Drosophila S2 cells, an established cell line, and it cleaved plasma proteins, including prophenoloxidase, serpin-2, and βGRP-2. Although it does not cleave all insect plasma proteins, thermolysin also processed mammalian plasma proteins. The most valuable advance in this work is showing that thermolysin operates within a physiological context, within plasma on circulating proteins. We infer that thermolysin is a potent element of bacterial pathogenesis. Autophagy, first discovered in the 1960s, is an evolutionarily conserved process that occurs in all eukaryotic cells. It is involved in fundamental processes in development and host defense. Autophagy (from the term autophagocytosis, for “self” and “eat”) is the basic mechanism for intracellular breakdown of cellular components, either to clear out unusable cell components or promote survival during times of energy emergencies. The process involves forming an autophagosome to isolate targets components and fusion with a lysosome for final degradation. In insects autophagy operates during metamorphosis and in host defense. Autophagy is controlled by autophagy-related (Atg) proteins encoded by ATG genes, known from many organisms, including insects. There are several ATG genes, designated as ATG1, ATG2, and so on. Tindwa et al., in Professor Yeon-Soo Han’s laboratory, report on two autophagy genes, ATG3 and ATG5 in the beetle, Tenebrio molitor. They report the complete sequences of both genes, and show that these genes are expressed throughout development in most tissues, particularly fat body and hemocytes. Archives of Insect Biochemistry and Physiology
Preface
r
3
Their key finding is that silencing these two genes by dsRNA treatments reduced survival of the beetle larvae challenged with the intracellular pathogen, Listeria monocytogenes. The significance of this work is the broadening of our appreciation of insect immune reactions to intracellular pathogens. We hope the papers in this Special Issue are of interest to a wide readership. The AIIS was planned to be held at Korea, China, or Japan in a rotating manner every other year following this groundbreaking symposium in 2014. The upcoming symposium is scheduled in China during 2016. We look forward to seeing you there. Guest Editors: Bok Luel Lee Busan National University, Busan, Korea Shun-Ichiro Kawabata Kyushu University, Fukuoka, Japan Chengshu Wang CAS, Shanghai Institutes, Biological Sciences, China Coordinating Editor: Yonggyun Kim Andong National University, Andong, Korea
Archives of Insect Biochemistry and Physiology
