Priming of indirect defence responses in maize is shown to be genotype-specific

Priming is an induced defence mechanism in which plants that have been exposed to elicitors, such as herbivore-induced plant volatiles (HIPVs), go into an alert state with faster and stronger responses against a future biotic challenge. This study evaluated whether HIPVs emitted by maize genotypes after herbivory by fall armyworm (Spodoptera frugiperda) larvae could prime neighbouring maize plants for an enhanced indirect defence response, and if priming was consistent across different genotypes. Two genotypes were selected based on their differences in HIPV emission: Sintético Spodoptera (SS), a relatively high emitter of HIPVs, and L3, a relatively low emitter of HIPVs. SS plants that were previously exposed to SS HIPVs initiated earlier and enhanced volatile production upon larval challenge, compared to SS plants that were previously exposed to SS undamaged plant volatiles. In addition, SS plants exposed to SS HIPVs and then to larval challenge attracted an egg parasitoid, Telenomus remus, at an earlier stage than SS plants that were only subjected to larval challenge, indicating a priming effect. There was no evidence of a priming response by L3 plants that were previously exposed to L3 or SS HIPVs. When comparing the gene expression of HIPV-exposed and undamaged plant volatile (UDV)-exposed plants, jasmonate-induced protein GRMZM2G05154 and UDP-glucosyltransferase bx8 genes related to the biosynthesis of DIBOA-Glu were upregulated. These data indicate that priming by HIPVs enhances indirect defence in maize plants as reported by other studies, and provide new information showing that the priming effect can be genotype-specific

Variability in herbivore-induced defence signalling across different maize genotypes impacts significantly on natural enemy foraging behaviour.

'Smart' plants that release volatile defence compounds in response to pest damage, and which recruit beneficial natural enemies, offer an opportunity for exploiting biological control in future crop protection strategies. Using six maize genotypes, Zapalote Chico (?landrace?), Mirt2A, Sintético Spodoptera (SS), L3, and two commercial hybrids BRS 4103 and BRS 1040, the aim of this work was to evaluate maize responses to larval damage from the fall armyworm Spodoptera frugiperda, a major maize pest in Brazil, and the ability of the egg parasitoid Telenomus remus to respond to HIPVs induced by S. frugiperda damage. Y-tube olfactometer bioassays with T. remus showed preferential responses to the S. frugiperda-induced volatiles of SS and BRS 4103 compared to constitutive volatiles of the same genotypes, but to none of the other genotypes tested. Chemical analysis of maize volatile extracts showed that SS produced more volatile compounds in response to S. frugiperda damage, followed by BRS 4103. In addition, higher levels of mono, homo-, or sesquiterpenes, together with green leaf volatiles (GLVs) were the most attractive blend for T. remus; however, there was no attraction when only GLVs were produced in higher levels. In summary, these results show that volatile defence signalling produced by maize plants due to S. frugiperda damage varies significantly depending on maize genotype and this variability influences T. remus foraging behaviour

Priming of indirect defence responses in maize is shown to be genotype-specific.

Na publicação: Marcos M. C. Costa; Maria Carolina Blassioli-Moraes

On a Clique-Based Integer Programming Formulation of Vertex Colouring with Applications in Course Timetabling

Vertex colouring is a well-known problem in combinatorial optimisation, whose alternative integer programming formulations have recently attracted considerable attention. This paper briefly surveys seven known formulations of vertex colouring and introduces a formulation of vertex colouring using a suitable clique partition of the graph. This formulation is applicable in timetabling applications, where such a clique partition of the conflict graph is given implicitly. In contrast with some alternatives, the presented formulation can also be easily extended to accommodate complex performance indicators (``soft constraints'') imposed in a number of real-life course timetabling applications. Its performance depends on the quality of the clique partition, but encouraging empirical results for the Udine Course Timetabling problem are reported

Variability in herbivore-induced defence signalling across different maize genotypes impacts significantly on natural enemy foraging behaviour

‘Smart’ plants that release volatile defence compounds in response to pest damage, and which recruit beneficial natural enemies, offer an opportunity for exploiting biological control in future crop protection strategies. Using six maize genotypes, Zapalote Chico (‘landrace’), Mirt2A, Sintético Spodoptera (SS), L3, and two commercial hybrids BRS 4103 and BRS 1040, the aim of this work was to evaluate maize responses to larval damage from the fall armyworm Spodoptera frugiperda, a major maize pest in Brazil, and the ability of the egg parasitoid Telenomus remus to respond to HIPVs induced by S. frugiperda damage. Y-tube olfactometer bioassays with T. remus showed preferential responses to the S. frugiperda-induced volatiles of SS and BRS 4103 compared to constitutive volatiles of the same genotypes, but to none of the other genotypes tested. Chemical analysis of maize volatile extracts showed that SS produced more volatile compounds in response to S. frugiperda damage, followed by BRS 4103. In addition, higher levels of mono, homo-, or sesquiterpenes, together with green leaf volatiles (GLVs) were the most attractive blend for T. remus; however, there was no attraction when only GLVs were produced in higher levels. In summary, these results show that volatile defence signalling produced by maize plants due to S. frugiperda damage varies significantly depending on maize genotype and this variability influences T. remus foraging behaviour

Trafficking through COPII Stabilises Cell Polarity and Drives Secretion during Drosophila Epidermal Differentiation

BACKGROUND: The differentiation of an extracellular matrix (ECM) at the apical side of epithelial cells implies massive polarised secretion and membrane trafficking. An epithelial cell is hence engaged in coordinating secretion and cell polarity for a correct and efficient ECM formation. PRINCIPAL FINDINGS: We are studying the molecular mechanisms that Drosophila tracheal and epidermal cells deploy to form their specific apical ECM during differentiation. In this work we demonstrate that the two genetically identified factors haunted and ghost are essential for polarity maintenance, membrane topology as well as for secretion of the tracheal luminal matrix and the cuticle. We show that they code for the Drosophila COPII vesicle-coating components Sec23 and Sec24, respectively, that organise vesicle transport from the ER to the Golgi apparatus. CONCLUSION: Taken together, epithelial differentiation during Drosophila embryogenesis is a concerted action of ECM formation, plasma membrane remodelling and maintenance of cell polarity that all three rely mainly, if not absolutely, on the canonical secretory pathway from the ER over the Golgi apparatus to the plasma membrane. Our results indicate that COPII vesicles constitute a central hub for these processes