Brachypodium distachyon grain: identification and subcellular localization of storage proteins

Seed storage proteins are of great importance in nutrition and in industrial transformation because of their functional properties. Brachypodium distachyon has been proposed as a new model plant to study temperate cereals. The protein composition of Brachypodium grain was investigated by separating the proteins on the basis of their solubility combined with a proteomic approach. Salt-soluble proteins as well as salt-insoluble proteins separated by two-dimensional gel electrophoresis revealed 284 and 120 spots, respectively. Proteins from the major spots were sequenced by mass spectrometry and identified by searching against a Brachypodium putative protein database. Our analysis detected globulins and prolamins but no albumins. Globulins were represented mainly by the 11S type and their solubility properties corresponded to the glutelin found in rice. An in silico search for storage proteins returned more translated genes than expressed products identified by mass spectrometry, particularly in the case of prolamin type proteins, reflecting a strong expression of globulins at the expense of prolamins. Microscopic examination of endosperm cells revealed scarce small-size starch granules surrounded by protein bodies containing 11S globulins. The presence of protein bodies containing glutelins makes B. distachyon closer to rice or oat than to wheat endosperm

Panmictic structure of the genetic diversity of apomictic Meloidogyne nematodes (Nematoda: Tylenchida)

Species delineation in parthenogenetic tropical species of Meloidogyne nematodes is particularly difficult although they are strictly apomictic. In fact, parthenogenesis in Meloidogyne nematodes is a recent phenomenon and the structure of the genetic diversity is mainly explained by crosses prior to the establishment of parthenogenesis. Under such hypothesis, increasing the size of a characterized sample by adding individuals should result in the decrease of the diversity structure. Twelve individuals from different geographical origins were added to the initial pool of 26 lines characterized in a previous study and an AFLP study was conducted on the whole set of 38 lines. As expected under the panmixy hypothesis, this resulted in a loss of genetic structure. This confirms thus that the genetic structure of tropical parthenogenetic Meloidogyne is due to crosses anterior to the establishment of apomixy

Effect of pyoverdine supply on cadmium and nickel complexation and phytoavailability in hydroponics

International audienceSiderophores are chelators with a high selectivity for Fe(III) and a good affinity for divalent metals, including Cd(II) and Ni(II). Inoculation with siderophore-producing bacteria (SPB) has thus been proposed as an alternative to chelator supply in phytoremediation. Accurate assessments of the potential of this association require a dissection of the interaction of siderophores with metals at the soil–root interface. This study focuses on pyoverdine (Pvd), the main siderophore produced by Pseudomonas aeruginosa. We first assessed the ability of Pvd to coordinate Ni(II). The stability constant of Pvd–Ni(II) (log K L′Ni = 10.9) was found to be higher than that of Pvd–Cd(II) (log K L′Cd = 8.2). We then investigated the effect of a direct supply of Pvd on the mobilization, speciation, and phytoavailability of Cd and Ni in hydroponics. When supplied at a concentration of 50 μM, Pvd selectively promoted Ni mobilization from smectite. It decreased plant Ni and Cd contents and the free ionic fractions of these two metals, consistent with the free ion activity model. Pvd had a more pronounced effect for Ni than for Cd, as predicted from its coordination properties. Inoculation with P. aeruginosa had a similar effect on Ni phytoavailability to the direct supply of Pvd