Hordoindolines are Predominantly Expressed in the Aleurone Layer in Late Kernel Development in Barley

Abstract

In order to isolate grain-specific genes during kernel development, two differential screening methods—suppression subtractive hybridization (SSH) and differential hybridization (DH)—were applied. Two cDNAs encoding hordoindolines known to be related to grain hardness were isolated and designated as Hordeum vulgare indoline a and b (HvIDa and HvIDb). The cDNAs encoding HvIDa and HvIDb contained a 450 bp and a 444 bp open reading frame (ORF) that encoded the putative hordoindoline-a and -b precursors consisting of 150 and 148 amino acids, respectively. The deduced amino acid sequences of both HvIDa and HvIDb contained one tryptophan-rich domain and ten highly conserved cysteine residues. The expression of the HvIDa gene was high at 5 DAF, reached a peak at 8 DAF and decreased slightly until 20 DAF, while the expression of HvIDb began to be detectable at 8 DAF when it was higher than that of other developmental stages and decreased slightly until 20 DAF. The HvIDa and HvIDb genes were predominantly detected in the aleurone cell layers in the late part of kernel development, e.g. at 20 DAF. These findings may provide clues to the molecular mechanisms of kernel development and contribute to the determination of the grain texture in barley.