Under the Barley Skin.

Dr. Chiara Campoli
Dr. Chiara Campoli

Understanding the mechanisms underlying caryopsis/hull adhesion in barley at the University of Dundee

Three years ago, I started working as a postdoc at the University of Dundee, Division of Plant Sciences, based at the James Hutton Institute. My project aimed to understand the role of variation in cuticular waxes accumulation during barley adaptation to different environments by studying a set of 79 barley eceriferum (cer) mutants impaired in cuticular waxes biosynthesis and accumulation.

During this project, I noticed that cer mutants frequently showed poor hull/seed caryopsis attachment. Barley grain exists in two forms: 'covered', where the hulls stick firmly to the seed and 'naked' , where the hulls shed free. Naked and covered barley actually represent extremes in a spectrum which includes intermediate phenotypes where adhesion is weak rather than absent, causing a phenomenon called 'skinning'. Three mutants, cer-yl, cer-ym and cer-zv, were reported as having naked grain (Barley Genetic Newsletter Vol 26, 1996), but no hull adhesion defect had been described for the other lines. To further explore this association, I screened the set of cer mutants for skinning and assembled a panel of nearly-isogenic lines exhibiting variation in hull adherence (Figure 1). While skinning is sensitive to the environment and to harvest and post-harvest management, more recent varieties show a genotype-dependent increase of skinning. Therefore, mutants are the ideal tool to understand the genetic basis of skinning while minimizing the confounding effects of the environment.

Skinning phenotype of the BWNIL <i>cer</i> mutants Skinning phenotype of the BWNIL cer mutants

This panel and our preliminary results formed the basis of a recently awarded BBSRC project to study the mechanisms underlying variation in barley hull adhesion, led by lead PI Dr.Sarah McKim at the University of Dundee, with the co-PI contribution of Prof.Robbie Waugh, and Dr.Luke Ramsay from the James Hutton Institute, and where I am the Researcher co-Investigator. The project started in April 2018 and will: (1) define the chemical and ultrastructural surface changes associated with hull adhesion and how they are altered by skinning loci; (2) reveal changes in gene expression at global and tissue-specific level associated with skinning and, finally, (3) identify novel cer genes, explore their contribution to skinning in modern barley cultivars, and develop diagnostics for use in breeding.

Although I have changed topic several times through my career, one thing has remained constant: barley mutants. Like many other researchers of the barley community I have to be extremely grateful for this wonderful available resource developed mainly through the 50s, 60s and 70s. I first studied the albina and xantha mutants, impaired in chloroplast development, and investigated which signals were going through the chloroplast during cold acclimation. Then I worked with flowering time mutants, identifying genes that contribute to photoperiodic flowering and circadian clock regulation. Three years ago I started working with cer mutants and the impact of cuticular waxes on adaptation. What I find particularly exciting about this new project is the prospect to find a link between one of the classic morphological features of barley and a problem affecting modern barley varieties which has a strong financial impact on the malting industry and growers.

Dr. Chiara Campoli - ResearchGate, Profile at Dundee University

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