Down-regulation of photosystem I by Erwinia carotovora-derived elicitors correlates with H(2)O(2) accumulation in chloroplasts of potato.

SUMMARY Identification of Solanum tuberosum genes responsive to culture filtrates (CF) from Erwinia carotovora ssp. carotovora resulted in isolation of psaD, a nuclear gene encoding the PSI-D subunit of photosystem I (PSI). This gene was rapidly and markedly down-regulated in CF-treated or wounded plants. Down-regulation of psaD transcripts was also triggered by signal molecules involved in plant defence such as methyl jasmonate. The CF-induced down-regulation of psaD transcripts was correlated with an accumulation of hydrogen peroxide in chloroplasts and a down-regulation of the NADP(+) photoreduction activity mediated by PSI. These results suggest that the CF-induced down-regulation of PSI may be related to the accumulation of reactive oxygen species in chloroplasts of plant cells responding to E. c. carotovora.