Identification of Two Plastid-Targetedβ-Amylases in Rice

Two β-amylase genes,OsBAM2andOsBAM3, are involved in starch remobilization in rice leaf sheaths

“…These findings show that BAM3 is a β-amylase isoform that functions predominantly in starch degradation in A. thaliana leaves and that BAM1 also plays an important role in this process, at least in the absence of BAM3 (Fulton et al, 2008). In contrast, in rice, although two β-amylase isoforms, OsBAM2 and OsBAM3, have been reported to be plastid-targeted active enzymes (Hirano et al, 2011), it is still unclear whether OsBAM2 and OsBAM3 are actually involved in starch remobilization in rice leaves.…”

“…In the rice genome, there are nine genes predicted to encode β-amylase-like proteins (Hirano et al, 2011;Saika et al, 2005). Of these genes, at least OsBAM2 and OsBAM3…”

“…Total RNA was purified from germinating seeds, leaf blades at the active tillering stage, leaf sheaths at the active tillering stage, leaf sheaths at 10-14 days after heading, and developing caryopses at 10-14 days after heading, following the procedures described by Hirano et al (2011). The purified total RNA (1 μg) was reverse-transcribed using SuperScript TM III Reverse Transcriptase (Life Technologies) with 50 pmol of Oligo(dT) 20 Primer (Life Technologies).…”

“…A serial dilution series of plasmid DNA containing the partial cDNAs of the genes was prepared to construct a standard curve. The mRNA level estimated from the standard curve was standardized to the expression of OsEF1α1 (RAP-ID: Os03g0177400) (Hirano et al, 2011;Sugimura et al, 2015), which encodes the translation elongation factor 1A.…”

“…Of the nine genes predicted to encode β-amylase isoforms annotated in the rice genome, OsBAM1 (RAP-ID: Os07g0543300) and OsBAM7 (RAP-ID: Os07g0667100) were expressed specifically in germinating seeds and developing caryopses, respectively (Hirano et al, 2011). Accordingly, we initially analyzed the transcript levels of β-amylase genes other than OsBAM1 and OsBAM7 in several organs.…”