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Elife ; 62017 11 24.
Artigo em Inglês | MEDLINE | ID: mdl-29171835


Highly adapted herbivores can phenocopy two-component systems by stabilizing, sequestering and reactivating plant toxins. However, whether these traits protect herbivores against their enemies is poorly understood. We demonstrate that the western corn rootworm Diabrotica virgifera virgifera, the most damaging maize pest on the planet, specifically accumulates the root-derived benzoxazinoid glucosides HDMBOA-Glc and MBOA-Glc. MBOA-Glc is produced by D. virgifera through stabilization of the benzoxazinoid breakdown product MBOA by N-glycosylation. The larvae can hydrolyze HDMBOA-Glc, but not MBOA-Glc, to produce toxic MBOA upon predator attack. Accumulation of benzoxazinoids renders D. virgifera highly resistant to nematodes which inject and feed on entomopathogenic symbiotic bacteria. While HDMBOA-Glc and MBOA reduce the growth and infectivity of both the nematodes and the bacteria, MBOA-Glc repels infective juvenile nematodes. Our results illustrate how herbivores combine stabilized and reactivated plant toxins to defend themselves against a deadly symbiosis between the third and the fourth trophic level enemies.

Antibiose , Benzoxazinas/metabolismo , Besouros/fisiologia , Glucosídeos/metabolismo , Herbivoria/fisiologia , Toxinas Biológicas/metabolismo , Animais , Zea mays/parasitologia
Plant Cell Environ ; 37(11): 2613-22, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24762051


Upon attack by leaf herbivores, many plants reallocate photoassimilates below ground. However, little is known about how plants respond when the roots themselves come under attack. We investigated induced resource allocation in maize plants that are infested by the larvae Western corn rootworm Diabrotica virgifera virgifera. Using radioactive (11) CO(2), we demonstrate that root-attacked maize plants allocate more new (11) C carbon from source leaves to stems, but not to roots. Reduced meristematic activity and reduced invertase activity in attacked maize root systems are identified as possible drivers of this shoot reallocation response. The increased allocation of photoassimilates to stems is shown to be associated with a marked thickening of these tissues and increased growth of stem-borne crown roots. A strong quantitative correlation between stem thickness and root regrowth across different watering levels suggests that retaining photoassimilates in the shoots may help root-attacked plants to compensate for the loss of belowground tissues. Taken together, our results indicate that induced tolerance may be an important strategy of plants to withstand belowground attack. Furthermore, root herbivore-induced carbon reallocation needs to be taken into account when studying plant-mediated interactions between herbivores.

Adaptação Fisiológica , Carbono/metabolismo , Besouros/fisiologia , Herbivoria/fisiologia , Raízes de Plantas/fisiologia , Zea mays/parasitologia , Animais , Biomassa , Metabolismo dos Carboidratos , Meristema/fisiologia , Raízes de Plantas/crescimento & desenvolvimento , Brotos de Planta/fisiologia , Caules de Planta/fisiologia , Água , Zea mays/fisiologia , beta-Frutofuranosidase/metabolismo
Methods Mol Biol ; 1097: 247-73, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24639163


Many methods have been proposed for RNA secondary structure comparison, and new ones are still being developed. In this chapter, we first consider structure representations and discuss their suitability for structure comparison. Then, we take a look at the more commonly used methods, restricting ourselves to structures without pseudo-knots. For comparing structures of the same sequence, we study base pair distances. For structures of different sequences (and of different length), we study variants of the tree edit model. We name some of the available tools and give pointers to the literature. We end with a short review on comparing structures with pseudo-knots as an unsolved problem and topic of active research.

Biologia Computacional/métodos , Conformação de Ácido Nucleico , RNA/química , Alinhamento de Sequência/métodos , Análise de Sequência de RNA/métodos , Algoritmos
BMC Bioinformatics ; 11: 222, 2010 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-20433706


BACKGROUND: A widely used method to find conserved secondary structure in RNA is to first construct a multiple sequence alignment, and then fold the alignment, optimizing a score based on thermodynamics and covariance. This method works best around 75% sequence similarity. However, in a "twilight zone" below 55% similarity, the sequence alignment tends to obscure the covariance signal used in the second phase. Therefore, while the overall shape of the consensus structure may still be found, the degree of conservation cannot be estimated reliably. RESULTS: Based on a combination of available methods, we present a method named planACstar for improving structure conservation in structural alignments in the twilight zone. After constructing a consensus structure by alignment folding, planACstar abandons the original sequence alignment, refolds the sequences individually, but consistent with the consensus, aligns the structures, irrespective of sequence, by a pure structure alignment method, and derives an improved sequence alignment from the alignment of structures, to be re-submitted to alignment folding, etc.. This circle may be iterated as long as structural conservation improves, but normally, one step suffices. CONCLUSIONS: Employing the tools ClustalW, RNAalifold, and RNAforester, we find that for sequences with 30-55% sequence identity, structural conservation can be improved by 10% on average, with a large variation, measured in terms of RNAalifold's own criterion, the structure conservation index.

RNA/química , Alinhamento de Sequência , Análise de Sequência de RNA , Algoritmos , Sequência de Bases , Bases de Dados Factuais , Dados de Sequência Molecular , Conformação de Ácido Nucleico