Barley lys3 mutants are unique amongst shrunken-endosperm mutants in having abnormally large embryos

Frederick Cook,Aoife Hughes,Candida Nibau,Beata Orman-Ligeza,Nicole Schatlowski,Cristobal Uauy,Kay Trafford

doi:10.1016/j.jcs.2018.04.013

Abstract

Many shrunken endosperm mutants of barley (Hordeum vulgare L.) have been described and several of these are known to have lesions in starch biosynthesis genes. Here we confirm that one type of shrunken endosperm mutant, lys3 (so called because it was first identified as a high-lysine mutant) has an additional phenotype: as well as shrunken endosperm it also has enlarged embryos. The lys3 embryos have a dry weight that is 50–150% larger than normal. Observations of developing lys3 embryos suggest that they undergo a form of premature germination and the mature lys3 grains show reduced dormancy. In many respects, the phenotype of barley lys3 is similar to that of rice GIANT EMBRYO mutants (affected in the OsGE gene). However, the barley orthologue of OsGE is located on a different chromosome from Lys3. Together these results suggest that the gene underlying Lys3 is unlikely to encode a starch biosynthesis protein but rather a protein influencing grain development.

Highlights

Cereal grains consist of three genetically-distinct parts: endosperm, embryo and pericarp
Measurements of grain and embryo weights confirmed that Risø1508, Risø18, M1460 and Risø19LE have large embryos compared to their wild-type controls (Table 1)
We have shown that all four mutants with lesions in the Lys3 locus have large embryos and that most other shrunkenendosperm mutants do not have large embryos

Summary

Introduction

Cereal grains consist of three genetically-distinct parts: endosperm, embryo and pericarp. The nutritive value of grains depends on other minor grain components such as proteins, amino acids, oils, vitamins and minerals. In barley (Hordeum vulagre L.), as in most cereals, lysine content (as a free amino acid or as a constituent of proteins) is limiting for nutritive value (Galili and Amir, 2013). For this reason, at the Risø Institute in Denmark in the 1960-70s, mutagenized barley germplasm was screened for altered lysine content and a number of high-lysine (lys) mutants were identified (Doll et al, 1974; Doll, 1976).

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