Functional characterization of Dihydroflavonol 4-reductase-like1 (DRL1) homologs in plant male gametophyte development

Abstract

The process of pollen development in higher plants is a complex strategy involving a diverse range of genes and interactions of gene products. However, little is known about the genes involved in the biosynthesis of the phenolic constituents of pollen wall. Previously, we have reported an anther-specific DRL1 (Dihydroflavonol 4-reductase-like1) gene in Arabidopsis, which is essential for pollen development and male fertility. However, its role in pollen development has not been fully characterized. Using the native promoter and a functional enhanced yellow fluorescent protein fusion to analyze the temporal and spatial expression of AtDRL1, we demonstrated that the DRL1: eYFP fusion protein is localized within the tapetum and is expressed in a developmentally regulated manner during early microsporogenesis. Moreover, the expression of the DRL1: eYFP fusion protein in drl1 homozygous mutants can complement the phenotype and restore seed formation. Another DRL1 homolog from tobacco was designated NtDRL1. Its full coding sequence and promoter region were isolated by RT-PCR and TAIL-PCR respectively. NtDRL1 expression was only detected in the developing tobacco anther, especially in stage -1 to 2, which corresponding to the meiosis and young microspore stage. In situ hybridization analysis showed NtDRL1 was expressed only in the tapetum layer of anther. Based on the analysis of the gene and protein expression profiles, DRL1 homolog genes are finely regulated during anther development and play a critical role in production of viable pollen. However, the detailed biochemical functions of DRL1 homologs remain unknown. Due to the high sequence homology, DRL1 homologs may be involved in a common biosynthesis pathway of phenolic compounds.