Molecular characterization of a cDNA encoding disulfide isomerase during barley kernel development

We conducted differential hybridization using two different tissues (caryopses as a tester and pericarps as a driver) 14 days after fertilization (DAF) to characterize the molecular mechanisms inherent to barley kernel development. Genes that were predominantly expressed in caryopsis were then sequenced and divided into nine categories based on their putative functions. The transcripts of Hordeum vulgare disulfide isomerase (HvPDI), a cDNA encoding disulfide isomerase, were detected in abundance in the caryopses but were expressed only weakly in the pericarps, stems, and leaves. Additionally, expression of HvPDI was abundant in 5-DAF kernels; however, its expression gradually decreased to 20 DAF. In situ hybridization revealed that HvPDI transcripts were detected primarily in the starch endosperm, located near the aleurone layer, during the later stages of kernel development (i.e., 14 and 20 DAF). The HvPDI gene was up-regulated as a result of several different plant hormone treatments, including treatment with ABA, GA₃, benzyladenine, and methyl jasmonate. These findings provide insight into the molecular mechanisms inherent in kernel development and assembly of seed storage proteins for accumulation into caryopses.