Cell-type-specific expression of a wheat-germ agglutinin gene in embryos and young seedlings of Triticum aestivum

Wheat germ agglutinin is a biomarker of whole grain content in wheat flour and pasta

When consumed as whole grain, wheat has a high nutrient density that contributes to a healthy diet. Yet, products labeled as whole wheat can still contain a substantial amount of refined grain leading to the confusion for consumers, so a method was designed to determine the whole grain status within wheat-based foods. Wheat germ agglutinin (WGA), a lectin found in the germ tissue of wheat kernels, was evaluated as a biomarker of whole grain wheat. WGA content strongly correlated with the percentage of whole wheat within premade mixtures of whole and refined (white) flours. Then, commercial flours labeled as whole wheat were tested for WGA content and found to contain up to 40% less WGA compared to a whole grain standard. Commercial pasta products labeled as whole wheat were also tested for WGA content and found to contain up to 90% less WGA compared to a whole grain standard. The differences in WGA content were not likely due to varietal differences alone, as the WGA content in common varieties used in domestic wheat flour production varied less than 25%. The levels of other constituents in wheat kernels, including starch, mineral, phytate, and total protein, were not different among the commercial whole wheat flours and pasta products. WGA is a unique biomarker that can identify wheat products with the highest whole grain content. PRACTICAL ABSTRACT: Whole grain wheat has a high nutrient density that can be part of a healthy diet, but products labeled as whole wheat can still contain some refined grain. Wheat germ agglutinin (WGA) was tested as a biomarker to measure whole grain status in wheat-based foods and revealed that some commercial whole wheat flour and pasta contained unexpectedly lower levels of the WGA biomarker compared to a whole grain standard. WGA may therefore be a useful way to test for whole grain wheat content.

Evaluation of Parkia pendula lectin mRNA differentially expressed in seedlings

Parkia pendula (Willd.) Walp. (Fabaceae) is a neotropical species of the genus Parkia more abundantly distributed in Central to South America. From the seeds of P. pendula a glucose/mannose specific lectin (PpeL) was isolated that has been characterised and used as a biotechnological tool but until now this is the first manuscript to analyse P. pendula mRNA expression in seedlings. For this porpoise a Differential display reverse transcription polimerase chain reaction (DDRT-PCR) was used to evaluate the expression of P. pendula lectin mRNAs in non-rooted seedlings. No bands were observed in the agarose gel, indicating the absence of mRNA of PpeL seedlings. our findings confirm that lectins mRNAs are differently regulated among species even if they are grouped in the same class.

Nonradioactive in situ hybridization for detection of hydrophobin mRNA in the phytopathogenic fungus Claviceps purpurea during infection of rye

Hydrophobins are unique fungal extracellular proteins that produce amphipathic films at interfaces, mediate contact to hydrophobic surfaces and are known to be important in phytopathogenicity. In the pathogenic ascomycete Claviceps purpurea, causing ergot disease in grasses and cereals and ergotism in livestock, a gene encoding an extraordinary type of hydrophobin has been detected, which appeared to be induced during alkaloid synthesis in axenic culture of an ergot-alkaloid producing strain of Claviceps (V. Garre and P. Tudzynski, pers. communication; Arntz and Tudzynski, 1997, Curr. Genet. 31, 357-360). To elucidate presence and function of this hydrophobin during infection of rye, the nonradioactive in situ hybridization technique was successfully adapted to the fungal organism and optimized in the pathogenic interaction system. Semithin cryosections proved to be suitable for microscopical gene expression analysis using immune-mediated alkaline-phosphatase staining for detection of digoxigenin-labeled cRNA probes. Specific hybridization of the prepared antisense riboprobe to hydrophobin mRNA was confirmed in nonradioactive Northern blots. While permeabilization by proteinase K had only a minor effect, the inclusion of detergent into the hybridization solutions enhanced specific RNA-RNA hybridization under maximum stringency. Hydrophobin mRNA was found in fungal cells, growing in axenic culture. In the disease cycle, hydrophobin transcripts were localized in abundance during vegetative fructification in conidiophores that actively produced conidia. No signals were observed in sclerotial hyphae during formation of the alkaloid-containing ergots, although they fluoresced intensely during total RNA detection using acridine orange. Notably, in situ hybridization experiments resulted in specific signals during early infection and colonization phases in the external mycelia and in hyphae penetrating the host epidermal layer. The presumed role of the hydrophobin gene product in ergot pathogenicity is discussed with respect to the described spatio-temporal distribution of the hydrophobin transcripts.

An embryo-specific protein of barley (Hordeum vulgare)

An immunological approach has been used to identify embryo-specific products that can be used as molecular markers of embryogenesis. Immunoadsorption of antisera to remove antigens common to embryos, meristematic cells and callus, revealed one major embryo-specific antigen, a polypeptide of 17 kDa. The antigen appeared at mid-stages of zygotic embryo formation and remained at similar levels up to six days post-germination of the seedling. The polypeptide could not be detected by protein staining, suggesting it is a non-abundant product. Appearance of the antigen could be induced by culture of zygotic embryos in vitro on abscisic acid (1 microM) or mannitol (9% mass/vol.). Cross-reactive products of near-identical molecular mass were observed in embryos of wheat, rye and oats but not distantly related cereals, nor embryos from dicotyledonous species. The timing of the appearance of the antigen was different in embryos formed from microspores during anther culture in vitro. In the cultured material, the 17-kDa polypeptide preceded the appearance of morphologically distinct embryonic structure.

Abscisic acid enhances the transcription of wheat-germ agglutinin mRNA without altering its tissue-specific expression

We used RNA gel-blot analysis, in-situ hybridization, and nuclear run-on transcription to examine the effects of exogenous abscisic acid (ABA) on the spatial distribution of mRNA for the lectin wheat-germ agglutinin (WGA) in developing wheat (Triticum aestivum L. cv. Marshall) embryos and seedlings. When analyzed by RNA gel blots, both developing embryos and seedlings exhibited higher steady-state levels of WGA mRNA after ABA treatment. As determined by in-situ hybridization, incubation of developing embryos in 0.1 mM ABA resulted in accumulation of WGA mRNA in the epidermal and subepidermal cell layers of the radicle and seminal roots and throughout the rootcap and coleorhiza. This spatial distribution was identical to that in control embryos. Nuclear run-on transcription assays indicated that at least part of this increase is attributable to transcriptional induction. Thus, exogenous ABA is capable of inducing increased WGA mRNA accumulation only in cells where it is expressed during normal embryogenesis. When seeds were germinated in the absence of ABA, WGA mRNA was detected only in the rootcap. In contrast, seeds imbibed and germinated in the presence of ABA for 3 d exhibited a spatial distribution of WGA mRNA similar to that observed in developing embryos treated with ABA. In contrast, when ABA was added to 3-d-old seedlings, WGA mRNA was not detected in regions of the root beyond the rootcap. We conclude that exogenous ABA, when applied continuously from imbibition, causes retention of the embryo-specific pattern of WGA mRNA distribution and that the spatial pattern of WGA mRNA expression in roots does not change when ABA is added after germination.