A comparison of aleurone cells in centenarian African and contemporary barley seeds to identify the geographic origin

Barley (Hordeum vulgare L.) is one of the main domesticated cereals. For this reason, barley seeds have been found in numerous archaeological sites, and since the mid-19th century have been available in numerous natural museum collections. About a hundred years ago samples were collected in the African countries of Eritrea and Cyrenaica (now Libya), and have been preserved as ex-situ in the museum collection “L’Orientale” of the University of Naples. The varieties of contemporary barley selected for comparative analysis were grown in Tuscany and are used in the production of craft beer. To ascertain their vitality, the ancient and contemporary seeds were placed in Petri dishes to hydrate under a sterile hood at room temperature after a sterilization procedure. Morphological and ultrastructural observations performed on the aleurone cells of the ancient samples presented vital cells. The extraction and purification of DNA from seeds produced results while the genotype comparison of ancient and contemporary barley varieties enabled the construction of a dendrogram of similarity, useful in describing barley from museum genetic heritage collections and in providing a molecular imprint of extant varieties.

Transcriptional regulatory activity of the cereal grain bZip protein TaABF1 can be either stimulated or inhibited by phosphorylation

The wheat bZip transcription factor TaABF1 mediates both abscisic acid (ABA)-induced and ABA-suppressed gene expression. As levels of TaABF1 protein do not change in response to ABA, and TaABF1 is in a phosphorylated state in vivo, we investigated whether TaABF1 could be regulated at the post-translational level. In bombarded aleurone cells, a TaABF1 protein carrying phosphomimetic mutations (serine to aspartate) at four sites (S36D, S37D, S113D, S115D) was three to five times more potent than wild-type TaABF1 in activating HVA1, an ABA-responsive gene. The phosphomimetic mutations also increased the ability of TaABF1 to downregulate the ABA-suppressed gene Amy32b. These findings strongly suggest that phosphorylation at these sites increases the transcriptional regulatory activity of TaABF1. In contrast to the activation observed by the quadruple serine to aspartate mutation, a single S113D mutation completely eliminated the ability of TaABF1 to upregulate HVA1 or downregulate Amy32b. Thus phosphorylation of TaABF1 can either stimulate or inhibit the activity of TaABF1 in regulating downstream genes, depending on the site and pattern of phosphorylation. Mutation of S318 and S322 (in the bZIP domain) eliminated the ability of TaABF1 to activate HVA1, but had no effect on the ability of TaABF1 to downregulate Amy32b, suggesting that TaABF1 represses Amy32b expression through a mechanism other than direct DNA binding. An important step towards understanding how ABA and gibberellin (GA) signals are integrated through TaABF1 phosphorylation to regulate downstream gene expression is to clarify the effects of those hormones on the expression of specific genes. In contrast to some other ABA-induced genes, we found that HVA1 induction by ABA or TaABF1 is not inhibited by GA.

The Effect of Globular Protein from Aleurone Cells of Barley on Stearic Acid Monolayers

Aleurone cells of barley accumulate the major storage globular protein, which is deposited in different patterns, such as protein and lipid self-assemblies. To better understand the complexity of storage self-assemblies, a fatty acid is chosen as a lipid model, namely stearic acid, SA, because of its high stability in monolayers at the air/aqueous solutions interface. The effect of aleurone cell protein, AC protein, on the phase behavior and surface structure of SA monolayers at the air/water interface has been studied by a combined Langmuir and Langmuir-Blodgett (LB) technique and by atomic force microscopy (AFM) investigation. The AC protein and SA monolayers were transferred on glass support, at several controlled surface pressures, characteristic for both the condensed liquid and solid phase of pure SA monolayers. The results indicate that globular particles of AC protein adsorb on and penetrate into and specifically interact with SA monolayers stabilizing the lipid/protein interface by achieving highly ordered self-assemblies, which may also occur within aleurone layers. These structures might play an important role both in aleurone cell development and in seedling growth.