Analysis of the two nodulins, sucrose synthase and ENOD2, in transgenic Lotus plants

Abstract

A partial sucrose synthase clone was isolated from a nodule cDNA library of Lotus japonicus, which had strong homology to sucrose synthase genes from Vicia faba and other plant species. The transcript was 2.7 kb in size and expression was enhanced in nodules compared to roots of L. japonicus. Two overlapping genomic clones containing sucrose synthase sequences were isolated from L. japonicus with a view to mapping and analysing the promoter of this gene. The early nodulin ENOD2 is a (hydroxy)proline-rich cell wall protein, which is expressed in the inner cortex surrounding the infected region of root nodules. In order to see if this nodulin is involved in the operation of the oxygen diffusion barrier, L. corniculatus was transformed with antisense ENOD2 gene constructs derived from the promoter and coding sequence of soybean. Two of the 20 antisense plant lines had significantly lower dry weight and nitrogenase activity as well as a different O2 profile through the nodules when compared to control plant lines, but there was no difference in ENOD2 transcriptional activity between the control and antisense plants. Possible reasons for this observation are discussed.Peer reviewe

Spatial and Temporal Organization of Sucrose Metabolism in Lotus japonicus Nitrogen-Fixing Nodules Suggests a Role for the Elusive Alkaline/Neutral Invertase

“…In contrast, accumulation of LjInv2 gene transcripts was at least 10-fold lower, in mature nodules, in comparison to LjInv1. A search of public nucleotide databases revealed the presence of at least two sucrose synthase coding sequences in L. japonicus, representing different 3¢-UTRs, designated LjSus3 (TC3979) and LjSus1 (Skot et al 1996). Quantitative RT-PCR analysis of LjSus3 revealed a 3.5-fold induction in nitrogen-fixing nodules compared to uninfected roots and flowers.…”