Age-dependent differential iron deficiency responses of rosette leaves during reproductive stages in Arabidopsis thaliana

Iron (Fe) is essential for plant development throughout the life cycle. Rosette leaves are responsive to Fe supply in Arabidopsis thaliana . Little is known about the dynamics of Fe deficiency (-Fe) responses of rosette leaves during the reproductive stages. We studied the dynamics of Fe-dependent responses at four consecutive reproductive stages (rosette, bolting, flowering, mature silique stages, hereby named RS, BS, FS, MS). We examined the growth of rosette leaves, elemental contents and gene expression patterns of Fe homeostasis genes belonging to differently regulated groups. We determined individual leaf sizes during seven days of +Fe and -Fe treatment at the RS. Young leaves responded to -Fe with growth inhibition and yellowing. Old and young leaves differed in gene expression patterns and elemental contents. Differences were noted between the early and late reproductive stages (primarily RS and BS versus MS) and correlations between ionomic contents and gene expression were detected. All leaves had induced Fe recycling genes at -Fe.

Our findings highlight a developmental stage-dependent modulation of +Fe and -Fe responses in leaves. We discuss possible leaf signaling mechanisms accounting for the distinct responses between old and young leaves. This insight is informative to strengthen our understanding on plant iron management.