In contrast to other cereals, typical barley cultivars have caryopses with adhering hulls at maturity, known as covered (hulled) barley. However, a few barley cultivars are a free-threshing variant called naked (hulless) barley. The covered/naked caryopsis is controlled by a single locus (nud) on chromosome arm 7HL. On the basis of positional cloning, we concluded that an ethylene response factor (ERF) family transcription factor gene controls the covered/naked caryopsis phenotype. This conclusion was validated by (i) fixation of the 17-kb deletion harboring the ERF gene among all 100 naked cultivars studied; (ii) two x-ray-induced nud alleles with a DNA lesion at a different site, each affecting the putative functional motif; and (iii) gene expression strictly localized to the testa. Available results indicate the monophyletic origin of naked barley. The Nud gene has homology to the Arabidopsis WIN1/SHN1 transcription factor gene, whose deduced function is control of a lipid biosynthesis pathway. Staining with a lipophilic dye (Sudan black B) detected a lipid layer on the pericarp epidermis only in covered barley. We infer that, in covered barley, the contact of the caryopsis surface, overlaid with lipids to the inner side of the hull, generates organ adhesion.caryopsis ͉ domestication ͉ epidermis ͉ ethylene response factor ͉ grass B arley (Hordeum vulgare L.) is the world's fourth most important cereal crop behind wheat, rice, and maize. A particular botanical feature of domesticated barley is that most cultivars have covered (hulled) caryopses in which the hull (outer lemma and inner palea) is firmly adherent to the pericarp epidermis at maturity; but a few cultivars are of a free-threshing variant called naked (hulless) barley (Fig. 1). No other Poaceae (grass) family crops show such hull-caryopsis adhesion. Both caryopsis types of barley have agronomic value and are used for different purposes. Covered barley is mainly used as an animal feed and for brewing. The hull of covered barley protects embryos from damage during mechanical harvest, and it also provides a filtration medium in separation of fermentable extract (wort) during malt processing (1). In contrast, naked barley is preferred for human food, because extensive pearling to remove the hull is unnecessary. Now that healthy effects of the soluble-fiber-rich barley products have been officially approved (2, 3), consumers' current interest in nutrition might boost the status of barley as human food.Easy processing of edible part can be a primary character of selection during domestication of a food crop (4, 5). Consequently, the naked caryopsis is considered a key domestication character in barley (5-8). The wild progenitor of barley, H. vulgare subsp. spontaneum, has covered grains. The covered grain is therefore considered adaptive in the wild: the hulls protect the caryopses from various biotic and abiotic stresses, and the awn attached to the distal end of the lemma facilitates seed dispersal and burial (9). According to archeological evidence (4)...

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The physiological roles of PAs (putrescine, spermidine, and spermine) were investigated for their ability to confer salt tolerance (200 mM NaCl, 48 h) in mung bean seedlings (Vigna radiata L. cv. BARI Mung-2). Salt stress resulted in Na toxicity, decreased K, Ca, Mg, and Zn contents in roots and shoots, and disrupted antioxidant defense system which caused oxidative damage as indicated by increased lipid peroxidation, H2O2 content, O2•- generation rate, and lipoxygenase activity. Salinity-induced methylglyoxal (MG) toxicity was also clearly evident. Salinity decreased leaf chlorophyll (chl) and relative water content (RWC). Supplementation of salt affected seedlings with exogenous PAs enhanced the contents of glutathione and ascorbate, increased activities of antioxidant enzymes (dehydroascorbate reductase, glutathione reductase, catalase, and glutathione peroxidase) and glyoxalase enzyme (glyoxalase II), which reduced salt-induced oxidative stress and MG toxicity, respectively. Exogenous PAs reduced cellular Na content and maintained nutrient homeostasis and modulated endogenous PAs levels in salt affected mung bean seedlings. The overall salt tolerance was reflected through improved tissue water and chl content, and better seedling growth.

We investigated the roles of exogenously applied Spd (0.3 mM spermidine) in alleviating Al (AlCl, 0.5 mM, 48 and 72 h)- induced injury in mung bean seedlings (Vigna radiata L. cv. BARI Mung-2). Aluminum toxicity induced oxidative damage overproducing reactive oxygen species (ROS; HO and O), increasing lipoxygenase activity and membrane lipid peroxidation. The toxic compound methylglyoxal (MG) also overproduced under Al stress. In order to circumvent Al-induced oxidative stress, enzymatic and non-enzymatic antioxidant defense were activated by the application of exogenous Spd. Exogenous Spd increased ascorbate (AsA) and glutathione (GSH) content, AsA/dehydroascorbate (DHA) ratio, GSH/ glutathione disulfide (GSSG) ratio, activity of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR) and catalase (CAT) which reduced ROS production and oxidative stress under Al stress. Spd-induced improvement of GSH pool and Gly II activity alleviated injurious effects of MG. Exogenous Spd positively modulated the endogenous PAs level. Regulating the osmoprotectant molecule (proline), Spd improved plant water status under Al stress. Exogenous Spd was potent to prevent breakdown of Al-induced photosynthetic pigment and to improve growth performances under Al stress. The mechanism by which Spd enhances antioxidant and glyoxalase components might be studied extensively. Spermidine-induced protection of photosynthetic pigment from damages and growth enhancement were remarkable and recommended for further detailed study to understand the mechanism.

High temperature and drought stress often occur simultaneously, and due to global climate change, this kind of phenomenon occurs more frequently and severely, which exerts devastating effects on plants. Polyamines (PAs) play crucial roles in conferring abiotic stress tolerance in plants. Present study investigated how exogenous pretreatment of spermine (Spm, 0.2 mM) enhances mung bean (Vigna radiata L. cv. BARI Mung-2) seedlings tolerance to high temperature (HT, 40 °C) and drought [induced by 5 % polyethyleneglycol (PEG)] stress individually and in combination. Spm pretreatment reduced reactive oxygen species (ROS) production including HO and O, lipoxygenase (LOX) activity, and membrane lipid peroxidation (indicated by malondialdehyde, MDA) under HT and/or drought stress. Histochemical staining of leaves with diaminobenzidine and nitro blue tetrazolium chloride also confirmed that Spm-pretreated seedlings accumulated less HO and O under HT and/or drought stress. Spermine pretreatment maintained the ascorbate (AsA) and glutathione (GSH) levels high, and upregulated the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) which were vital for imparting ROS-induced oxidative stress tolerance under HT and/or drought stress. The cytotoxic compound methylglyoxal (MG) was overproduced due to HT and/or drought, but exogenous Spm pretreatment reduced MG toxicity enhancing the glyoxalase system. Spermine pretreatment modulated endogenous PA levels. Osmoregulation and restoration of plant water status were other major contributions of Spm under HT and/or drought stress. Preventing photosynthetic pigments and improving seedling growth parameters, Spm further confirmed its influential roles in HT and/or drought tolerance.