Cadmium affects the expression of ELF4, a circadian clock gene in Arabidopsis

The transcript abundance of clock-associated genes in Arabidopsis thaliana was monitored in a time point experiment, in plants treated with cadmium (Cd) for 24 h and upon two weeks Cd exposure and maintained in 12-h light/12-h dark cycles. The mRNA abundance of several molecular components associated with the circadian clock was modulated by Cd in plants treated for 24 h. In particular the CIRCADIAN CLOCK ASSOCIATED1 (CCA1), LATE ELONGATED HYPOCOTYL (LHY), TIMING OF CAB EXPRESSION1 (TOC1), EARLY FLOWERING3 (ELF3) and EARLY FLOWERING4 (ELF4) exhibited an amplified transcription peak and GIGANTEA (GI) showed a postponed and increased mRNA peak. Short-term Cd treatment did not affect the transcription level of CONSTANS (CO) or ZEITLUPE (ZTL). Long-term Cd exposure did not alter rhythmicity and expression amplitude with the exception of ELF4 that showed higher RNA abundance in plants Cd treated. In addition, measurement of flowering time in wild-type and ELF4-overexpressing plants exposed to Cd indicated that it is not altered by the environmental stress posed by Cd toxicity. The ELF4 promoter study indicated that this gene is expressed in leaves as well as in stamen, abscission and dehiscence zones. Long-term Cd exposure significantly modified ELF4 expression in these organs. The presence of this metal in polluted sites could therefore impact plant responsiveness to photoperiod and temperature and hence developmental decisions.

► We describe Cd effects on the expression of circadian clock genes in Arabidopsis thaliana.
► Cd effect on flowering time was measured in WT and ELF4-overexpressing plants.
► ELF4 promoter study allowed to localize ELF4 expression in specific organs.
► Transcript modulations induced by Cd was monitored in those organs.