Abstract
The aleurone is a critical component of the cereal seed and is located at the periphery of the starchy endosperm. During germination, the aleurone is responsible for releasing hydrolytic enzymes that degrade cell wall polysaccharides and starch granules, which is a key requirement for barley malt production. Inter- and intra-species differences in aleurone layer number have been identified in the cereals but the significance of this variation during seed development and germination remains unclear. In this study, natural variation in mature aleurone features was examined in a panel of 33 Hordeum vulgare (barley) genotypes. Differences were identified in the number of aleurone cell layers, the transverse thickness of the aleurone and the proportion of aleurone relative to starchy endosperm. In addition, variation was identified in the activity of hydrolytic enzymes that are associated with germination. Notably, activity of the free fraction of β-amylase (BMY), but not the bound fraction, was increased at grain maturity in barley varieties possessing more aleurone. Laser capture microdissection (LCM) and transcriptional profiling confirmed that HvBMY1 is the most abundant BMY gene in developing grain and accumulates in the aleurone during early stages of grain fill. The results reveal a link between molecular pathways influencing early aleurone development and increased levels of free β-amylase enzyme, potentially highlighting the aleurone as a repository of free β-amylase at grain maturity.
Highlights
Barley (Hordeum vulgare L.) is recorded as one of the first agricultural crops to be domesticated[1] and is a major food source in both Asia and northern Africa
Larger grains contain more aleurone, mainly as a result of increased aleurone width, but smaller grains contain more aleurone layers with a higher proportion of aleurone relative to starchy endosperm. These results indicate that mature aleurone morphology in barley is determined by the number and size of aleurone cells, which are in turn influenced by starchy endosperm development, and the contribution of each feature can vary depending on the genotype
We utilised autofluorescence microscopy to identify differences in aleurone morphology within a panel of diverse barley genotypes, and considered how these differences relate to grain biology and the amount of germination-related enzyme activity
Summary
Barley (Hordeum vulgare L.) is recorded as one of the first agricultural crops to be domesticated[1] and is a major food source in both Asia and northern Africa. Barley grain contains many key nutrients, antioxidants and dietary fibres that benefit the human diet[6,7,8] Most of these nutrients accumulate in the endosperm, a filial tissue that supports embryonic growth in addition to providing physical protection during seed development[9]. The embryo releases gibberellic acid (GA), which translocates to the aleurone where it induces the transcription of genes encoding hydrolytic enzymes[15] Enzymes, such as 1,3;1,4-β-glucanase (β-glucanase), α-amylase and β-amylase, are released to catalyse the breakdown of cell wall polysaccharides and starchy energy reserves that are essential for germination and the production of malt for brewing. Intra-species variation has been found between barley cultivars, and several QTL were identified in an Erhard Frederichen × Criolla Negra population that influence the number of aleurone layers[23]. Transcriptional profiling of fresh and laser micro-dissected grain tissues was used to ascertain when and where key germination-related genes are transcribed during grain development
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
