Latex is an endogenous milky fluid synthesized and accumulated under pressure in a network of laticifer cells. In this study, latices from five plant species were examined for deterrent effect on oviposition of two Coleoptera (Bruchidae) pests. The latex from Euphorbia tirucalli, Calotropis procera and Plumeria rubrae exhibited deterrent activity on oviposition of both Callosobruchus maculatusand Zabrotis subfasciatus beetles. The latex from Cryptostegia grandiflora and Himathantus drasticus were less effective to C. maculatus and Z. subfasciatus oviposition, respectively. Eggs laid on latex-treated seeds were not affected.The emergence and the mean time of development and weight of larvae grown in treated seeds were similar to the controls. The deterrent activity of C. procera and P. rubra was dose and time-dependent for Z. subfasciatus rather than to C. maculatus. The deterrent effect was completely eliminated if the whole latices were fractionated in protein fractions, rubber and small metabolites. Exposing insects to crude latices did not alter ovipostion on untreated seeds. These RESULTSsuggest that latices possess deterrent activity on insect oviposition mediated by a repellent effect, but that proteins and volatile substances are probably not involved. The repellent-like activity can be considered as a defensive role played by these fluids that relies on the combined action of their components.

Seeds from fifty native Amazonian Fabaceae species (representing subfamilies Caesalpinioideae, Mimosoideae and Faboideae) were screened for the presence of new lectins. Their crude protein extracts were assayed for hemagglutinating activity (HA). The protein fractions of Anadenanthera peregrina, Dimorphandra caudata, Ormosia lignivalvis and Swartzia laevicarpa exhibited HA, and this activity was inhibited by galactose or lactose but not by glucose or mannose. The crude extract of S. laevicarpa exhibited HA activity only after ion exchange chromatography, and its lectin was further purified by affinity chromatography on immobilized lactose. Despite the large number of lectins that have been reported in leguminous plants, this is the first description of lectins in the genera Anadenanthera, Dimorphandra and Ormosia. The study of lectins from these genera and from Swartzia will contribute to the understanding of the evolutionary relationships of legume lectins in terms of their protein processing properties and structures.

In this study, proteins extracted from laticifer cells of three plants were examined by electrophoresis, mass spectrometry (MALDI-TOF) and characterized in respect of proteolytic, chitinolytic and anti-oxidative activities by means of zymography and colorimetric assays. Acidic proteins with molecular masses between 12.5 and 74.5 kDa predominated in laticifers of P. rubra. This profile was not found in laticifers of C. grandiflora and E. tirucalli. The later was poor in respect of proteins. Strong anti-oxidative activity of superoxide dismutase (E.C. 1.15.1.1) was detected in P. rubra and C. grandiflora latices, and to a lesser extent ascorbate peroxidase (E.C. 1.11.1.1) and isoforms of peroxidase were seen. Catalase (E.C. 1.11.1.6) was detected only in laticifer cells of C. grandiflora. Chitinase (E.C. 3.2.1.14) was the sole activity found in laticifer cells of E. tirucalli, but was also detected in the other latices. The strong proteolytic activity of C. grandiflora was shown to be shared by at least three distinct cysteine proteinases (E.C. 3.4.22.16). Serine, aspartic and metaloproteinases were not detected. In laticifer cells of P. rubra, four proteinases were detected, including cysteine and serine types. This study reports new protein data of laticifers from plants that have been poorly investigated in this respect and contributes to the understanding of biochemical and functional aspects of laticifers in plants.

It has been shown previously that the laticifer fluid of Calotropis procera (Ait.) R.Br. is highly toxic to the egg hatching and larval development of Aedes aegypti L. In the present study, the larvicidal potential of other laticifer fluids obtained from Cryptostegia grandiflora R.Br., Plumeria rubra L. and Euphorbia tirucalli L. was evaluated. We attempted to correlate larvicidal activity with the presence of endogenous proteolytic activity in the protein fraction of the fluids. After collection, the fluids were processed by centrifugation and dialysis to obtain the soluble laticifer protein (LP) fractions and eliminate water insoluble and low molecular mass molecules. LP did not visibly affect egg hatching at the doses assayed. LP from Cr. grandiflora exhibited the highest larval toxicity, while P. rubra was almost inactive. E. tirucalli was slightly active, but its activity could not be correlated to proteins since no protein was detected in the fluid. The larvicidal effects of LP from C. procera and Cr. grandiflora showed a significant relationship with the proteolytic activity of cysteine proteinases, which are present in both materials. A purified cysteine proteinase (papain) from the latex of Carica papaya (obtained from Sigma) was similarly effective, whereas trypsin and chymotrypsin (both serine proteinases) were ineffective. The results provide evidence for the involvement of cysteine proteinase activity in the larvicidal action of some laticifer fluids. C. procera is an invasive species found in areas infested with Ae. aegypti and thus could prove useful for combating mosquito proliferation. This is the first report to present evidence for the use of proteolytic enzymes as chemical agents to destroy Ae. aegypti larvae.

A composição bioquímica elementar de sementes de seis cultivares de feijão de corda (Vigna unguiculata) foi determinada e a fração lipídica de cada cultivar, caracterizada. Os resultados sugerem que todas as farinhas de semente compartilham composição bioquímica similar, embora as cultivares Br-14 e CE-315 difiram das Br-9 e Br-17 no teor de umidade. As frações lipídicas purificadas foram caracterizadas quanto ao teor e tipos de ácidos graxos presentes. A cultivar Br-17 possui alto conteúdo de ácido palmítico (58,2%) e o menor conteúdo de ácido linoléico (6,4%) enquanto a Vita 7 apresenta alto conteúdo de ácido linoléico (21,8%) e relativamente baixo conteúdo de ácido palmítico (41%) em uma base comparativa. Os ácidos graxos pentacosanóico e eicosanóico representam a fração lipídica menor e o primeiro não ocorre em CE-315. Os resultados sugerem que diferentes cultivares obtidas por melhoramento genético podem apresentar diferenças quantitativas e qualitativas na composição bioquímica; assim, diferenças na capacidade germinativa, resistência a predadores no campo de plantio e no armazenamento, poderiam estar relacionadas à inibição ou estímulo da expressão de genes codificadores da síntese de moléculas relevantes, que refletem diferenças de composição, como demonstrado neste trabalho.

The biochemical composition of the seeds of six bean - Vigna unguiculata (Walp) cultivars was determined and the lipid fraction of each of these cultivars was characterized. The results suggest that all analyzed seed flours share similar biochemical composition, although the cultivars Br-14 and CE-315 differ in relation to Br-9 and Br-17 in water content. The purified fatty acid fractions were characterized according to their lipid content. The cultivar Br-17 possesses high content of palmitic acid (58.2%) and low content of linoleic acid (6.4%) while Vita 7 possesses high contents of linoleic acid (21.8%) and relatively low content of palmitic acid (41%) on a comparative basis. Pentacosanoic and eicosanoic acids represent the minor fraction of lipids and the former does not occur in CE-315. The results suggest that different cultivars obtained by genetic combination may present relevant differences in their biochemical composition. Thus, differences in germination capacity, resistance to predators in the field or storage house may be related to over expression or inhibition of genes encoding synthesis of relevant molecules which refleet difference in composition as demonstrated in this study.