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

Iron is essential for plant development throughout the life cycle. When plants lack the crucial micronutrient iron (Fe), they develop interveinal leaf chlorosis and stunted growth. To cope with this, they adjust gene expression and manage Fe and other metal ions accordingly. Rosette leaves may act as Fe sources and Fe sinks. Little is known about the dynamics of Fe deficiency (-Fe) responses in the Arabidopsis thaliana 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 rapidly to -Fe with growth inhibition and yellowing. Old and young leaves differed in gene expression patterns and elemental contents. Differences were also noted between the early and late reproductive stages (primarily RS and BS versus MS) and correlations between ionomic contents and gene expression were detected. Although all leaves had induced Fe recycling genes at -Fe, the expression patterns of “High Fe” and other Fe marker genes together with elemental contents indicate that old leaves at the RS and BS might serve as Fe sources, while young leaves might be Fe sinks 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 for iron management in crops.

One-sentence summary

This study explores reproductive stage-dependent responses of rosette leaves to iron availability, revealing distinct growth, elemental contents, and gene expression patterns between young and old leaves and stages.

Major findings

• Young leaves but not old leaves exhibited rapid growth inhibition and chlorosis under -Fe conditions.

• Significant differences in gene expression and ionomics profile were observed between old and young leaves.

• Contrasts were noted between the early reproductive stages (RS, BS) and the late ones (FS, MS).

• Correlations between ionomics profiles and gene expression indicated a complex interaction.