Sedentary endoparasitic nematodes cause extensive damage to a large number of ornamental plants and food crops, with estimated economical losses over 100 billion US$ worldwide. Various efforts have put forth in order to minimize nematode damage, which typically involve the use of nematicides that have high cost and enhanced toxicity to humans and the environment. Additionally, different strategies have been applied in order to develop genetically modified plants with improved nematode resistance. Among the strategies are anti-invasion and migration, feeding-cell attenuation, and anti-nematode feeding. In the present study, we focus on anti-nematode feeding, which involves the evaluation and potential use of the cysteine proteinase (CPs) propeptide as a control alternative. The cysteine proteinase prodomain, isolated from Heterodera glycines (HGCP prodomain), is a natural inhibitory peptide used to transform soybean cotyledons using Agrobacterium rhizogenes. Genetically modified soybean roots expressing the propeptide were detected by Western blot and expression levels were measured by ELISA (around 0.3%). The transgenic roots expressing the propeptide were inoculated with a thousand H. glycines at the second juvenile stage, and a remarkable reduction in the number of females and eggs was observed. A reduction of female length and diameter was also observed after 35 days post-inoculation. Furthermore, the H. glycines mature protein was detected in females fed on soybean transformed root expressing or not expressing the propeptide. The data presented here indicate that the HGCP propeptide can reduce soybean cyst nematode infection and this strategy could be applied in the near future to generate resistant crop cultivars.

Acanthoscelides obtectus is a devastating storage insect pest capable of causing severe bean crop losses. In order to maintain their own development, insect pest larvae feed continuously, synthesizing efficient digestive enzymes. Among them, cysteine proteinases (CPs) are commonly produced as inactive precursors (procysteines), requiring a cleavage of the peptide proregion to become active. The proregion fits tightly into the active site of procysteines, efficiently preventing their activity. In this report, a CP cDNA (cpao) was isolated from A. obtectus midgut larvae. In silico studies indicated that the complete CP sequence contains a hydrophobic signal peptide, a prodomain and a conserved catalytic region. Moreover, the encoding cDNA contains 963bp translating into a 321 residue protein, CPAo, which was expressed in E. coli, fused with thioredoxin. Enzymatic assays using the recombinant protein revealed that the enzyme was catalytically active, being able to cleave the synthetic substrate Z-Phe-Arg-7-AMC. Additionally, this report also focuses the cpao propeptide (PCPAo) subcloning and expression. The expressed propeptide efficiently inhibited CPAo, as well as digestive CP of other bean bruchids. Little or no activity was found against proteolytic enzymes of two other coleopterans: Rhyzopertha dominica and Anthonomus grandis. The data reported here indicate the possibility of endogenous propeptides as a novel strategy on bruchids control, which could be applicable to bean improvement programs.

Marine macroalgae, Kappaphycus alvarezii has economic importance which is considered as the main source of Kappa carrageenan, a hydrocolloid used in various industries as an emulsifying agent and stabilizer. In the production process of this raw material, the fresh seaweed is subjected to grinding and filtering process, yielding a wet solid fraction rich in carrageenan and other liquid fractions. The latter has been studied for its use in pulverization of bean leaves, wheat, soybean, rice, among others. Several reports have shown positive effects on the growth, yield and quality of vegetables and grains treated with the extract of this alga. However, there are few reports on the use of the liquid extract of K. alvarezii for seed treatment, and also of its use in conjunction with the solid fraction of seaweed. In this context, this study aims to evaluate the physiological quality of soybean seeds treated with liquid extract of this alga and, with the mixture of liquid extract and solid biomass, submitted to a hydrolysis process. Two soybean seed treatment tests were performed in laboratory: one treatment contained pure liquid extract (100%) while the other was mixed with two samples of solid biomass hydrolyzed with concentrations of 25 and 75%. For comparison of their results, there was a positive control treatment and one negative control treatment. The results showed that, within the present working conditions, treatments with seaweed extract can increase the length of the aerial part of the seedling up to 28% and the length of the primary root up to 19% as compared to the negative control; thus, it improves the physiological performance of seeds.

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