Functional Characterization of an Amaranth Natterin-4-Like-1 Gene in Arabidopsis thaliana

The functional characterization of an Amaranthus hypochondriacus Natterin-4-Like-1 gene (AhN4L-1) coding for an unknown function protein characterized by the presence of an aerolysin-like pore-forming domain in addition to two amaranthin-like agglutinin domains is herewith described. Natterin and nattering-like proteins have been amply described in the animal kingdom. However, the role of nattering-like proteins in plants is practically unknown. The results described in this study, obtained from gene expression data in grain amaranth and from AhN4L-1-overexpressing Arabidopsis thaliana plants indicated that this gene was strongly induced by several biotic and abiotic conditions in grain amaranth, whereas data obtained from the overexpressing Arabidopsis plants further supported the defensive function of this gene, mostly against bacterial and fungal plant pathogens. GUS and GFP AhN4L-1 localization in roots tips, leaf stomata, stamens and pistils also suggested a defensive function in these organs, although its participation in flowering processes, such as self-incompatibility and abscission, is also possible. However, contrary to expectations, the overexpression of this gene negatively affected the vegetative and reproductive growth of the transgenic plants, which also showed no increased tolerance to salinity and water-deficit stress. The latter despite the maintenance of significantly higher chlorophyll levels and photosynthetic parameters under intense salinity stress. These results are discussed in the context of the physiological roles known to be played by related lectins and AB proteins in plants.

Plant morphometry matches beetle diversity: effects of natural adjacent vegetation on grain Amaranth crop under small-holder conditions

Grain Amaranth, Amaranthus hypochondriacus L., is an emerging arable crop cultivated worldwide. One way to obtain resources from the crop, other than grain, is to grow Amaranths in the dry season and harvest only the leaves. In this environmental condition the response of an Amaranth agroecosystem to the presence of natural and semi-natural habitats or other crops has not been studied yet. We analysed the response of (1) Amaranth morphometry and (2) alpha and beta diversity of beetles to the nearness of adjacent vegetation and natural habitats (such as deciduous forest) at the small-holder conditions. Our results showed that A. hypochondriacus crop plants responded positively to the presence of an ecotone (adjacent vegetation) and the natural habitat (deciduous forest), i.e., A. hypochondriacus plants grew bigger in the section nearest to adjacent vegetation, which was a pattern consistent in time. Moreover, for beetles (considered as a bioindicator group), richness was different amongst the study areas and negatively followed the gradient of perturbation. These results suggest that Amaranth crop is sensitive to the presence of natural and semi-natural habitats but not to other crops in the dry season. In addition, beetles match the response of Amaranth plants. This is the first time that this type of data is recorded in grain Amaranth agroecosystem and it will help to understand the interaction amongst grain Amaranth agroecosystems, biodiversity, and natural adjacent vegetation to boost ecosystem services.

Relationship of Cultivated Grain Amaranth Species and Wild Relative Accessions

Amaranthus is a genus of C4 dicotyledonous herbaceous plants, and three New World species have been domesticated to produce grain crops with light colored seed which are classified as pseudo-cereals rich in protein and minerals. A core collection of grain amaranths and immediate precursor species has been established, representing the closest related species. The goal of this study was to evaluate the genetic diversity in that collection of cultivated and wild species, using competitive allele single nucleotide polymorphism markers. A secondary objective was to determine the relationships among the three cultivated species and non-domesticated Amaranthus, while a third objective was to evaluate the utility of the markers in detecting diversity in the 276 genotypes. The markers were found to be highly variable with an average polymorphism information content of 0.365. All markers were bi-allelic; and the major allele frequency ranged from 0.388 to 0.871. Population structure analysis of the cultigens revealed the presence of two sub populations. Phylogeny confirmed that the two Mesoamerican species, Amaranthus cruentus and Amaranthus hypochondriacus, were related and distant from the South American species Amaranthus caudatus, which in turn was very closely clustered with Amaranthus quitensis, even though this is considered a weedy relative. The first pair of species were likely to have inter-crossed, while the latter two likely exist in a wild-cultivated hybrid state. In conclusion, the results of this SNP study provided insights on amaranth cultivars and their relationship to wild species, the probable domestication events leading to the cultivars, and possible crop breeding or germplasm conservation strategies.

Foliar Application of Flavonoids (rutin) Regulates Phytoremediation Efficiency of Amaranthus Hypochondriacus by Altering the Permeability of Cell Membranes and Immobilizing Excess Cd in the Cell Wall

The gap between the current serious soil heavy metal (HM) contamination situation and the low efficiency of soil remediation has become one of the factors limiting economic development and human health. The aim of this study was to propose a method to improve the efficiency of phytoremediation by exogenous rutin application and to explain the potential mechanism. A series of rutin treatments were designed to evaluate the biomass, cadmium (Cd) accumulation and phytoremediation efficiency responses of Amaranthus hypochondriacus to different levels of rutin (0.5, 1.5, and 5 ppm) under different Cd stress levels (10, 25, 50, and 100 ppm). The determination of cell membrane damage indicators, the subcellular distribution of Cd and the establishment of a predictive model for Cd accumulation were also carried out. The results showed a decline in cell membrane damage with rutin application, and more Cd ions were immobilized in the cell wall than in the vacuole, resulting in an increase in Cd tolerance in plants. The addition of rutin caused significant effects on the synthesis of glutathione (GSH), including the advancement of the conversion of GSH to phytochelatins (PCs). Among them, PC2 and PC3 in the leaves contributed the most to the high accumulation of Cd in Amaranthus hypochondriacus according to the prediction model. Overall, the phytoremediation efficiency and phytoextraction amount of Amaranthus hypochondriacus with foliar rutin application were improved significantly by 260% and 319%, respectively. These findings can contribute to the further development of soil remediation in Cd-contaminated fields.