Anthers Crave Copper

Yan et al. searched for proteins that regulate the delivery of the micronutrient copper to flowers to ensure successful reproduction

By Jiapei Yan, Ju-Chen Chia, and Olena Vatamaniuk

Background: Global food security and the demand for high-yielding grain crops necessitate the use of marginal lands for agriculture purposes. These soils are often deficient in essential mineral nutrients such as copper, causing reduced crop growth and infertility, and consequently low yield or even total crop failure. Scientists have already learned a great deal about how copper is absorbed from the soil by plant roots. However, we still do not know much about how copper moves throughout the plant, which reproductive structures require copper, and which transcriptional networks coordinate copper transport processes and plant reproduction.

Question: We wanted to know which reproductive organs of flowers accumulate copper, how copper is delivered there and how copper transport processes are regulated. We addressed these questions using the model plant Arabidopsis thaliana.

Findings: We identified a new protein, CITF1, whose transcript accumulates in A. thaliana flowers during copper deficiency. We found that CITF1 regulates copper uptake into roots and delivery to flowers and that anthers of flowers accumulate the most copper. We also found that CITF1 works together with another protein, SPL7, and both are needed to regulate copper uptake into plant roots and delivery to anthers. Loss of function of SPL7 and CITF1 in the citf1 spl7 double mutant leads to seedling lethality and pollen infertility. CITF1 and SPL7 also regulate the biosynthesis of jasmonic acid (JA), a plant hormone involved in stamen development, and JA is needed for normal plant growth under copper deficiency.

Next steps: We will now focus on establishing the mechanism by which CITF1 contributes to copper homeostasis and identifying the precise sites of copper action in pollen development and plant fertility, the transport systems responsible for copper delivery to reproductive organs, and the sites of interaction between copper and the jasmonate metabolic pathway.

Yan, J., Chia, J.C., Sheng, H., Jung, H.-I., Zavodna, T.-O., Zhang, L., Huang, R., Jiao, C., Craft, E.J., Fei, Z., Kochian, L.V., Vatamaniuk, O.K. (2017). Arabidopsis Pollen Fertility Requires the Transcription Factors CITF1 and SPL7 that Regulate Copper Delivery to Anthers and Jasmonic Acid Synthesis. The Plant Cell