ABSTRACT
A full-length cDNA clone, designated Ljca1, coding for a beta-type carbonic anhydrase (CA; EC: 4.2.1.1) was isolated from a Lotus japonicus nodule cDNA library. Semi-quantitative RT-PCR analysis revealed that Ljca1 codes for a nodule-specific CA, transcripts of which accumulate at maximum levels in young nodules at 14 days post-infection (d.p.i.). In situ hybridization and immunolocalization revealed that Ljca1 transcripts and LjCA1 polypeptides were present at high levels in all cell types of young nodules. In contrast, in mature nodules both transcripts and polypeptides were confined in a few cell layers of the nodules inner cortex. However, the central infected tissue of both young and mature nodules exhibited high CA activity, indicating the presence of additional CA isoforms of plant and/or microbial origin. This was supported by the finding that a putative Mesorhizobium loti CA gene was transiently expressed during nodule development. In addition, the temporal and spatial accumulation of phosphoenolpyruvate carboxylase (PEPC; EC: 4.1.1.31) was determined by semi-quantitative RT-PCR and immunolocalization. The results suggest that LjCA1 might fulfill different physiological needs during L. japonicus nodule development.
Subject(s)
Carbonic Anhydrases/genetics , Lotus/enzymology , Plant Roots/growth & development , Amino Acid Sequence , Bacteria/enzymology , Bacteria/genetics , Carbonic Anhydrases/physiology , Immunohistochemistry , Lotus/genetics , Molecular Sequence Data , Phylogeny , Plant Roots/metabolism , Symbiosis/genetics , Symbiosis/physiologyABSTRACT
LjSUT4, encoding a putative sucrose transporter, was identified in a Lotus japonicus nodule cDNA library. The deduced amino acid sequence showed a high degree of identity with sucrose transporters from other plants. Semi-quantitative RT-PCR analysis demonstrated that the L. japonicus SUT4 gene was expressed at high levels in both roots and nodules. In situ hybridization revealed that, in young nodules, SUT4 mRNA transcripts are present in vascular bundles, inner cortex and both infected and uninfected cells while, in mature nodules, accumulation of transcripts was restricted only in vascular bundles and the inner cortex. The results indicated that LjSUT4 codes for a putative sucrose transporter, and its expression pattern suggests a possible shift in the mechanism of sugar transport during nodule development. The role of this polypeptide in sucrose transport and metabolism is discussed.
