Molecular characterization and expression analysis of hemoglobin cDNA from small radish (Raphanus sativus L var.sativus)

Abstract

We have characterizedRSHb, a hemoglobin cDNA clone isolated from a seedling cDNA library of the small radish (Raphanus sativus L var.sativus). Its 480-bp ORF encodes a protein of 160 amino acids, with a predicted molecular weight of 17.98 kDa and an estimated pl of 8.77. Sequence analysis and multiple alignment revealed that theRSHb shares 95% nucleotide sequence and 93% amino acid sequence identities with those ofAHB 1 fromArabidopsis thaliana, a Class I non-symbiotic hemoglobin. Our Southern blot analysis showed thatRSHb is a single-copy gene in the small radish genome. The northern blot analysis demonstrated that this gene is expressed in all organs, including the roots, hypocotyls, and leaves, with transcription levels increasing under flooding and high-sucrose conditions. However, cold treatment does not affect its expression pattern. We conclude thatRSHb is a Class I non-symbiotic hemoglobin gene.