Evaluation of sodium tetraphenylboron (NaBPh4) as a soil test of potassium availability

Non-exchangeable potassium (K_nex) contributes to soil K availability and several extractants are used to access its contribution. This study evaluated sodium tetraphenylboron (NaBPh₄) as a soil test of K availability in 20 soils from Northern Greece. Winter wheat (Triticum aestivum L. var. ‘Yecora’) was sown in a greenhouse pot experiment and five cropping cycles were carried out until K-depletion. Soils were analyzed with NH₄OAc and NaBPh₄ (1 and 5 min incubation periods). Critical levels of K ranged between 130–140 and 330–340 mg K kg^?1 of soil for NH₄OAc and NaBPh₄ (1 min incubation period), respectively, and between 32 and 35 g K kg^?1 of wheat dry matter. NaBPh₄-K (1 min) related better with K concentration and uptake compared to NH₄OAc for each cropping cycle (r² = 0.45–0.83 and 0.44–0.89) and for all soils (r² = 0.58 and 0.51). Similar results obtained in soils low in exchangeable K (r² = 0.41 and 0.39). Correlation between NH₄Oac- and NaBPh₄-extractable K was weaker among soils below the critical level (r = 0.70) compared to those above (r = 0.93). Inclusion of illitic K and cation exchange capacity in a multiple linear regression between NH₄OAc- and NaBPh₄-extractable K showed that they significantly contributed to NaBPh₄-extractable K.     

Comparative genome and proteome analysis of Anopheles gambiae and Drosophila melanogaster

Comparison of the genomes and proteomes of the two diptera Anopheles gambiae and Drosophila melanogaster, which diverged about 250 million years ago, reveals considerable similarities. However, numerous differences are also observed; some of these must reflect the selection and subsequent adaptation associated with different ecologies and life strategies. Almost half of the genes in both genomes are interpreted as orthologs and show an average sequence identity of about 56%, which is slightly lower than that observed between the orthologs of the pufferfish and human (diverged about 450 million years ago). This indicates that these two insects diverged considerably faster than vertebrates. Aligned sequences reveal that orthologous genes have retained only half of their intron/exon structure, indicating that intron gains or losses have occurred at a rate of about one per gene per 125 million years. Chromosomal arms exhibit significant remnants of homology between the two species, although only 34% of the genes colocalize in small "microsyntenic" clusters, and major interarm transfers as well as intra-arm shuffling of gene order are detected.     

Malaria control with genetically manipulated insect vectors

At a recent workshop, experts discussed the benefits, risks, and research priorities associated with using genetically manipulated insects in the control of vector-borne diseases.     

Contribution of non-exchangeable potassium on its quantity-intensity relationships under K-depleted soils

ABSTRACT

Quantity-Intensity (Q/I) parameters were used for elucidating the role of buffering properties of soils through K depletion. Winter wheat was sown in a greenhouse pot experiment until K-depletion and soils were analyzed with NH₄OAc and NaBPh₄ (1 min incubation period). Q/I isotherms (partitioned in exchangeable and non-exchangeable form) were constructed for the soils before and at the end of the K-exhaustion experiment. Results showed that NaBPh₄-K correlated better than NH₄OAc-K with intensity parameter (AR_e^K) or labile K (-ΔΚ₀) in K-depleted soils (r = 0.41 and 0.70), indicating the importance of non-exchangeable K in K dynamics. The latter was confirmed from the comparison of buffering characteristics between initial and K-depleted soils which showed that among the soils studied there was a group whose increase in buffering capacity (PBC^K_t) was due to non-exchangeable K fixation. Furthermore, NaBPh₄-K was well predicted by the sum of exchangeable K and the quantity of K that has to be applied to achieve K balance as derived from Q/I isotherms (EK₀ + CK₀). Finally, relationships were found between Q/I parameters of the initial soils (-ΔΚ_0i, ΕΚ_0i, ΕΚ_ri, CK_0i) and the K-depleted ones (ΕΚ_rd, ΕΚ_0d, CK_0d, CK_rd) which allowed corresponding prediction of the initial parameters (r² = 0.78–0.87).     

Effects of mosquito genes on Plasmodium development

Malaria parasites must complete a complex developmental cycle in an Anopheles mosquito vector before transmission to a vertebrate host. Sexual development of the parasite in the midgut is initiated in the lumen immediately after the mosquito ingests infected blood, and the resulting ookinetes must traverse the surrounding epithelial layer before transforming into oocysts. The innate immune system of the mosquito is activated during midgut invasion, but to date, no evidence has been published identifying mosquito immune genes that affect parasite development. Here, we show by gene silencing that an Anopheles gambiae leucine rich-repeat protein acts as an antagonist and two C-type lectines act as protective agonists on the development of Plasmodium ookinetes to oocysts.     

Evolutionary dynamics of immune-related genes and pathways in disease-vector mosquitoes

Mosquitoes are vectors of parasitic and viral diseases of immense importance for public health. The acquisition of the genome sequence of the yellow fever and Dengue vector, Aedes aegypti (Aa), has enabled a comparative phylogenomic analysis of the insect immune repertoire: in Aa, the malaria vector Anopheles gambiae (Ag), and the fruit fly Drosophila melanogaster (Dm). Analysis of immune signaling pathways and response modules reveals both conservative and rapidly evolving features associated with different functional gene categories and particular aspects of immune reactions. These dynamics reflect in part continuous readjustment between accommodation and rejection of pathogens and suggest how innate immunity may have evolved.