Differential expression of maize sugar responsive genes in response to iron deficiency

Substractive screening of a root cDNA library from Fe deficient maize plants led to isolate a Sus1 cDNA encoding for sucrose synthase (UDP-glucose:D fructose 2-α-D-glycosyl-transferase, EC 2.4.1.13). Northern analysis showed that Sus1 mRNA abundance increased in response to iron deficiency in maize roots, whereas abundance of two other sugar responsive transcripts, Sh1 sucrose synthase and pZSS6 metallothionein mRNAs, decreased under these conditions. These mRNA abundance variations have been correlated to increased sugar concentrations in iron deficient maize roots. In contrast in maize leaves, glucose and fructose, but not sucrose content, decreased in response to iron deficiency. mRNA abundance of Sus1, but also of H1 and CS11 encoding for a histone and a cytoplasmic ribosomal proteins, respectively, was decreased in maize iron deficient leaf sheaths compared to iron sufficient plants. The general conclusion of this work points out a differential alteration of sugar metabolism and sugar responsive gene expression between leaves and roots in response to iron deficiency.