Conserved cis-acting motifs and localization of MFT2 transcripts and MFT2 protein in barley and rice

Abstract

Pre-harvest sprouting, in which grain germinates while still on the spikes, causes substantial yield and quality losses, particularly in regions where the rainy season and harvest times overlap. Breeders have used a natural mutation in the A-box motif in the promoter of wheat (Triticum aestivum) MFT2 gene on chromosome 3A (TaMFT-3A) to prevent pre-harvest sprouting in wheat cultivars in East Asia. Here, we examined the barley (Hordeum vulgare) and rice (Oryza sativa) orthologs of TaMFT-3A. RNA in situ hybridization showed that the rice and barley orthologs are primarily expressed in the scutellum, indicating that these three MFT2 genes have a common expression pattern during seed development. Analysis of the cis-acting regulatory elements of their promoter sequences showed that the promoters share eight seed-specific cis-acting RY motifs and a binding site for B3-domain transcription factors, the main regulators of seed development. Moreover, we found tandemly repeated A-box motifs in the promoters of TaMFT on chromosomes 3B and 3D, but a single motif on chromosome 3A, possibly explaining why the A-box motif mutation in TaMFT-3A increases dormancy. Our immunohistochemical observations of green fluorescent protein (GFP)-tagged MFT2 in transgenic rice plants detected rice MFT2 (OsMFT2)-GFP in the scutellum and the scutellar epithelium, which is an important tissue for initiating germination. These findings improve our understanding of the role of MFT2, providing information for reducing pre-harvest sprouting in cereals.