Abstract
The low-beta-amylase1 (lba1) mutant of Arabidopsis thaliana originally isolated as a mutant showing reduced level of sugar-induced expression of Atβ-Amy encoding the major β-amylase showed pleiotropic phenotypes such as early flowering, elongated seeds, short day-sensitive growth, glucose- and abscisic acid-hypersensitive and mannose-resistant germination. Determination of a 61 kb-long genomic sequence surrounding the lba1 loci identified a base mutation within a gene encoding AtUPF1 RNA helicase involved in nonsense-mediated mRNA decay (NMD) pathway controlling various post-transcriptional events. Expression of the 35S::AtUPF1 in the lba1 mutant partially rescued these phenotypes such as reduced sugar-induced expression of Atβ-Amy, early flowering, elongated seeds, hyper-sensitivity to glucose and ABA, and mannose-resistant germination. Insertion of T-DNA in the middle of the AtUPF1 gene caused seedling lethality which could be rescured by the introduction of 35S::AtUPF1. These results indicate that AtUPF1 is essential for growth of plants and plays important roles in various stages of plant development.
