EAGER: Investigating a novel role of a micronutrient copper in auxin metabolism and signaling in reproduction in A. thaliana

Cornell University, Ithaca NY

Investigators

Abstract

Global food security and the demand for high-yielding grain crops are among the most urgent and ambitious drivers of modern plant sciences due to the current trend of population growth and decreasing arable land resources. The total grain yield is directly linked to crop and soil fertility. In this regard, the limited availability of the micronutrient copper in the soil causes copper deficiency in crop plants. This condition leads to plant infertility and, consequently, low yields. However, the physiological, molecular, and genetic mechanisms underlying this trait are unknown. Besides copper nutritional demands, plant reproduction is regulated by plant hormones. Among them, the hormone auxin has a recognized role in reproductive organ development and patterning. The existence of the relationship between auxin-mediated developmental programs and plant mineral demands has not yet been considered. This project will use multifaceted functional genetics and genomic tools to explore a newly discovered untraditional link between copper function in reproduction and auxin in a model plant, Arabidopsis thaliana. The discoveries made through this award will guide future studies on the interplay between micronutrients and hormone signaling for ensuring normal plant developmental programs. In a broader context, this project is relevant to the future of food security, as it has the potential to contribute to molecular breeding efforts directed at improving crop grain yield on marginal soils. This project will provide unique training opportunities. Through a partnership with the University of Texas at El Paso (UTEP), students at Cornell and UTEP will get hands-on experience in using cutting-edge synchrotron X-ray techniques to address complex biological questions. Copper is a redox-active micronutrient with a recognized role in plant reproduction and seed yield. Despite this knowledge, the specific function of copper in reproduction, the sites of its action, and the genes controlling its delivery to reproductive organs still needed to be fully understood. The phytohormone auxin regulates every aspect of plant development and is a recognized morphogen that controls reproductive organ development and patterning. Previous work has shown that copper localizes to anthers, pistils, and pollen grains in Arabidopsis thaliana; copper delivery to these reproductive structures requires two transcription factors, CITF1 and SPL7. Failure to deliver copper to these reproductive structures in wild-type grown under acute copper deficiency or in a double mutant lacking CITF1 and SPL7 leads to female and male infertility. Notably, some fertility and shoot architecture defects of copper-deficient and citf1 spl7 mutant plants resembled those observed in auxin synthesis, transport, or signaling mutants. This finding was intriguing, considering that the existence of the relationship between auxin-mediated developmental programs and plant mineral demands has yet to be considered. The proposed studies will uncover whether copper and the CITF1-SPL7-regulated copper homeostatic pathway influence reproduction via acting on auxin metabolism and/or signaling, thereby presenting a radically different perspective on the mechanism of copper action in plant development. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.