Cen, Yijing

Abstract ‘Candidatus Liberibacter asiaticus’ (CLas), the causal agent of citrus huanglongbing, is transmitted by the Asian citrus psyllid Diaphorina citri. While CLas-positive (CLas+) females exhibit increased fecundity and metabolic demands, their neuroendocrine regulation remains unclear. We propose CLas manipulates dopamine (DA) signaling to enhance psyllid fecundity and CLas proliferation. Metabolomics revealed elevated DA in CLas+ females. Silencing DA synthesis genes and receptor DcDop2 via RNAi reduced lipid reserves, fecundity, and ovarian CLas titers. Through combined in vivo and in vitro experiments, we demonstrated that the microRNA miR-31a suppresses DcDop2 expression by binding to its 3’ untranslated region. Overexpression of miR-31a resulted in decreased DcDop2 expression and CLas titers in the ovaries, eliciting phenotypic defects akin to DcDop2 knockdown. Furthermore, DcDop2 knockdown and miR-31a overexpression reduced juvenile hormone (JH) levels and adipokinetic hormone (AKH) signaling in fat bodies and ovaries. Consequently, CLas hijacks the DA/DcDop2-miR-31a-AKH-JH signaling cascade to improve D. citri lipid metabolism and fecundity, while simultaneously promoting its replication. These findings suggest a mutualistic interaction between CLas proliferation and ovarian development within the insect host that enrich our understanding of the molecular interplay between plant pathogens and vector insects and offer novel targets and strategies for the field management of HLB.

AbstractThe severe Asiatic form of huanglongbing (HLB), caused by “Candidatus Liberibacter asiaticus” (CLas), threatens global citrus production via the citrus psyllid, Diaphorina citri. Culturing challenges of CLas necessitate reducing D. citri populations for disease management. CLas boosts the fecundity of CLas‐positive (CLas+) D. citri and fosters its own proliferation by modulating the insect host's juvenile hormone (JH), but the intricate endocrine regulatory mechanisms remain elusive. Here, it is reported that the D. citri ecdysis‐triggering hormone (DcETH) and its receptor DcETHR play pivotal roles in the reciprocal benefits between CLas and D. citri within the ovaries, influencing energy metabolism and reproductive development in host insects; miR‐210, negatively regulates DcETHR expression, contributing to this symbiotic interaction. CLas infection reduces 20‐hydroxyecdysone (20E) levels and stimulates DcETH release, elevating JH production via DcETHR, enhancing fecundity and CLas proliferation. Furthermore, circulating JH levels suppress 20E production in CLas+ ovaries. Collectively, the orchestrated functional interplay involving 20E, ETH, and JH increases energy metabolism and promotes the fecundity of CLas+ D. citri and CLas proliferation. These insights not only broaden the knowledge of how plant pathogens manipulate the reproductive behavior of insect hosts but also offer novel targets and strategies for combatting HLB and D. citri.

Diaphorina citri serves as the primary vector for ‘Candidatus Liberibacter asiaticus (CLas),’ the bacterium associated with the severe Asian form of huanglongbing. CLas-positive D. citri are more fecund than their CLas-negative counterparts and require extra energy expenditure. Therefore, understanding the molecular mechanisms linking metabolism and reproduction is of particular importance. In this study, we found adipokinetic hormone (DcAKH) and its receptor (DcAKHR) were essential for increasing lipid metabolism and fecundity in response to CLas infection in D. citri. Knockdown of DcAKH and DcAKHR not only resulted in the accumulation of triacylglycerol and a decline of glycogen, but also significantly decreased fecundity and CLas titer in ovaries. Combined in vivo and in vitro experiments showed that miR-34 suppresses DcAKHR expression by binding to its 3’ untranslated region, whilst overexpression of miR-34 resulted in a decline of DcAKHR expression and CLas titer in ovaries and caused defects that mimicked DcAKHR knockdown phenotypes. Additionally, knockdown of DcAKH and DcAKHR significantly reduced juvenile hormone (JH) titer and JH signaling pathway genes in fat bodies and ovaries, including the JH receptor, methoprene-tolerant (DcMet), and the transcription factor, Krüppel homolog 1 (DcKr-h1), that acts downstream of it, as well as the egg development related genes vitellogenin 1-like (DcVg-1-like), vitellogenin A1-like (DcVg-A1-like) and the vitellogenin receptor (DcVgR). As a result, CLas hijacks AKH/AKHR-miR-34-JH signaling to improve D. citri lipid metabolism and fecundity, while simultaneously increasing the replication of CLas, suggesting a mutualistic interaction between CLas and D. citri ovaries.

Diaphorina citri serves as the primary vector for ‘Candidatus Liberibacter asiaticus (CLas),’ the bacterium associated with the severe Asian form of huanglongbing. CLas-positive D. citri are more fecund than their CLas-negative counterparts and require extra energy expenditure. Therefore, understanding the molecular mechanisms linking metabolism and reproduction is of particular importance. In this study, we found adipokinetic hormone (DcAKH) and its receptor (DcAKHR) were essential for increasing lipid metabolism and fecundity in response to CLas infection in D. citri. Knockdown of DcAKH and DcAKHR not only resulted in the accumulation of triacylglycerol and a decline of glycogen, but also significantly decreased fecundity and CLas titer in ovaries. Combined in vivo and in vitro experiments showed that miR-34 suppresses DcAKHR expression by binding to its 3’ untranslated region, whilst overexpression of miR-34 resulted in a decline of DcAKHR expression and CLas titer in ovaries and caused defects that mimicked DcAKHR knockdown phenotypes. Additionally, knockdown of DcAKH and DcAKHR significantly reduced juvenile hormone (JH) titer and JH signaling pathway genes in fat bodies and ovaries, including the JH receptor, methoprene-tolerant (DcMet), and the transcription factor, Krüppel homolog 1 (DcKr-h1), that acts downstream of it, as well as the egg development related genes vitellogenin 1-like (DcVg-1-like), vitellogenin A1-like (DcVg-A1-like) and the vitellogenin receptor (DcVgR). As a result, CLas hijacks AKH/AKHR-miR-34-JH signaling to improve D. citri lipid metabolism and fecundity, while simultaneously increasing the replication of CLas, suggesting a mutualistic interaction between CLas and D. citri ovaries.

Abstract Diaphorina citri serves as the primary vector for ‘Candidatus Liberibacter asiaticus’ (CLas), the bacterium associated with the severe Asian form of huanglongbing. CLas-positive D. citri are more fecund than their CLas-negative counterparts and require extra energy expenditure. Therefore, understanding the molecular mechanisms linking metabolism and reproduction is of particular importance. In this study, we found adipokinetic hormone (DcAKH) and its receptor (DcAKHR) were essential for increasing lipid metabolism and fecundity in response to CLas infection in D. citri. Knockdown of DcAKH and DcAKHR not only resulted in the accumulation of triacylglycerol and a decline of glycogen, but also significantly decreased fecundity and CLas titer in ovaries. Combined in vivo and in vitro experiments showed that miR-34 suppresses DcAKHR expression by binding to its 3’ untranslated region, whilst overexpression of miR-34 resulted in a decline of DcAKHR expression and CLas titer in ovaries and caused defects that mimicked DcAKHR knockdown phenotypes. Additionally, knockdown of DcAKH and DcAKHR significantly reduced juvenile hormone (JH) titer and JH signaling pathway genes in fat bodies and ovaries, including the JH receptor, methoprene-tolerant (DcMet), and the transcription factor, Krüppel homolog 1 (DcKr-h1), that acts downstream of it, as well as the egg development related genes vitellogenin 1-like (DcVg-1-like), vitellogenin A1-like (DcVg-A1-like) and the vitellogenin receptor (DcVgR). As a result, CLas hijacks AKH/AKHR-miR-34-JH signaling to improve D. citri lipid metabolism and fecundity, while simultaneously increasing the replication of CLas, suggesting a mutualistic interaction between CLas and D. citri ovaries.

Abstract Diaphorina citri is the primary vector of the bacterium, ‘Candidatus Liberibacter asiaticus’ (CLas) associated with the severe Asian form of huanglongbing. CLas-positive D. citri are more fecund than their CLas-negative counterparts and require extra energy expenditure. Therefore, understanding the molecular mechanisms linking metabolism and reproduction is of particular importance. In this present study, we found adipokinetic hormone (DcAKH) and its receptor (DcAKHR) were essential for increased lipid metabolism and fecundity in response to CLas infection in D. citri. Knockdown of DcAKH and DcAKHR not only resulted in triacylglycerol accumulation and a decline of glycogen, but also significantly decreased fecundity and CLas titer in ovaries. Combined in vivo and in vitro experiments showed that miR-34 suppresses DcAKHR expression by binding to its 3’ untranslated region, whilst overexpression of miR-34 resulted in a decline of DcAKHR expression and CLas titer in ovaries and caused defects that mimicked DcAKHR knockdown phenotypes. In addition, knockdown of DcAKH and DcAKHR significantly reduced juvenile hormone (JH) titer and JH signaling pathway genes in fat bodies and ovaries, including the JH receptor, methoprene-tolerant (DcMet), and the transcription factor, Krüppel homolog 1 (DcKr-h1), that acts downstream of it, as well as the egg development related genes vitellogenin 1-like (DcVg-1-like), vitellogenin A1-like (DcVg-A1-like) and the vitellogenin receptor (DcVgR). As a result, CLas hijacks AKH/AKHR-miR-34-JH signaling to improve D. citri lipid metabolism and fecundity, while simultaneously increasing the replication of CLas, suggesting a mutualistic interaction in D. citri ovaries with CLas.

AbstractThe evolution of insect vector‐pathogen relationships has long been of interest in the field of molecular ecology. One system of special relevance, due to its economic impacts, is that between Diaphorina citri and ‘Candidatus Liberibacter asiaticus’ (CLas), the cause of the severe Asian form of huanglongbing. CLas‐positive D. citri are more fecund than their CLas‐negative counterparts, boosting opportunities for pathogens to acquire new vector hosts. The molecular mechanism behind this life‐history shift remains unclear. Here, we found that CLas promoted ovarian development and increased the expression of the vitellogenin receptor (DcVgR) in ovaries. DcVgR RNAi significantly decreased fecundity and CLas titer in ovaries, extended the preoviposition period, shortened the oviposition period and blocked ovarian development. Given their importance in gene regulation, we explored the role of miRNAs in shaping these phenotypes and their molecular triggers. Our results showed that one miRNA, miR‐275, suppressed DcVgR expression by binding to its 3' UTR. Overexpression of miR‐275 knocked down DcVgR expression and CLas titer in ovaries, causing reproductive defects that mimicked DcVgR knockdown phenotypes. We focused, further, on roles of the Juvenile Hormone (JH) pathway in shaping the observed fecundity phenotype, given its known impacts on ovarian development. After CLas infection, this pathway was upregulated, thereby increasing DcVgR expression. From these combined results, we conclude that CLas hijacks the JH signalling pathway and miR‐275, thereby targeting DcVgR to increase D. citri fecundity. These changes simultaneously increase CLas replication, suggesting a pathogen‐vector host mutualism, or a seemingly helpful, but cryptically costly life‐history manipulation.

AbstractDiaphorina citriserves as the primary vector for ‘CandidatusLiberibacter asiaticus’ (CLas), the bacterium associated with the severe Asian form of huanglongbing.CLas-positiveD. citriare more fecund than theirCLas-negative counterparts and require extra energy expenditure. Therefore, understanding the molecular mechanisms linking metabolism and reproduction is of particular importance. In this study, we found adipokinetic hormone (DcAKH) and its receptor (DcAKHR) were essential for increasing lipid metabolism and fecundity in response toCLas infection inD. citri.Knockdown ofDcAKHandDcAKHRnot only resulted in the accumulation of triacylglycerol and a decline of glycogen, but also significantly decreased fecundity andCLas titer in ovaries. Combinedin vivoandin vitroexperiments showed that miR-34 suppressesDcAKHRexpression by binding to its 3’ untranslated region, whilst overexpression of miR-34 resulted in a decline ofDcAKHRexpression andCLas titer in ovaries and caused defects that mimickedDcAKHRknockdown phenotypes. Additionally, knockdown ofDcAKHandDcAKHRsignificantly reduced juvenile hormone (JH) titer and JH signaling pathway genes in fat bodies and ovaries, including the JH receptor,methoprene-tolerant(DcMet), and the transcription factor,Krüppel homolog 1 (DcKr-h1), that acts downstream of it, as well as the egg development related genesvitellogenin 1-like(DcVg-1-like),vitellogenin A1-like(DcVg-A1-like) and the vitellogenin receptor (DcVgR). As a result,CLas hijacks AKH/AKHR-miR-34-JH signaling to improveD. citrilipid metabolism and fecundity, while simultaneously increasing the replication ofCLas, suggesting a mutualistic interaction betweenCLas andD. citriovaries.