Biology subjects

Chia, J.-C.

Publications and source records attributed to Chia, J.-C..

3 recordsLinked to original sources

bioRxiv2021

OPT3 plays a central role in both copper and iron homeostasis and signaling due to its ability to deliver copper as well as iron to the phloem in Arabidopsis

Copper and iron are essential micronutrients but are toxic when accumulating in cells in excess. Thus, their uptake by roots is tightly regulated. While plants sense and respond to local copper availability, the systemic regulation of copper uptake has not been documented. By contrast, both local and systemic control for iron uptake has been reported. Iron abundance in the phloem has been suggested to act systemically, regulating the expression of iron uptake genes in the root. Consistently, shoot-to-root iron signaling is disrupted in A. thaliana mutants lacking the phloem companion cell-localized iron transporter, AtOPT3: opt3 mutants overaccumulate iron in leaves while constitutively upregulating iron deficiency-responsive genes in roots. We report that AtOPT3 transports copper and mediates its delivery from source leaves to sinks including young leaves and developing embryos. Consequently, the opt3 mutant accumulates less copper in the phloem, is sensitive to copper deficiency, and mounts transcriptional copper deficiency response in roots. Copper rescues these defects. Notably, feeding the opt3 mutant with copper or iron via the phloem in leaves downregulates the expression of both copper and iron-deficiency marker genes in roots, suggesting that copper and iron can substitute each others function in the phloem in shoot-to-root communication. One-sentence summaryAtOPT3 loads copper and iron into the phloem companion cells, for subsequent distribution to sink tissues and systemic signaling of copper and iron deficiency.

plant biology↗

bioRxiv2020

Ferroportin 3 is a dual-targeted mitochondrial/chloroplast iron exporter necessary for iron homeostasis in Arabidopsis

Mitochondria and chloroplasts are organelles with high iron demand that are particularly susceptible to iron-induced oxidative stress. Despite the necessity of strict iron regulation in these organelles, much remains unknown about mitochondrial and chloroplast iron transport in plants. Here, we propose that Arabidopsis Ferroportin 3 (FPN3) is an iron exporter dual-targeted to mitochondria and chloroplasts. FPN3 is expressed in shoots regardless of iron conditions, but its transcripts accumulate under iron deficiency in roots. fpn3 mutants cannot grow as well as wild type under iron-deficient conditions and shoot iron levels are reduced in fpn3 mutants compared to wild type. ICP-MS measurements show that iron levels in the mitochondria and chloroplasts are increased relative to wild type, consistent with the proposed role of FPN3 as a mitochondrial/plastid iron exporter. In iron deficient fpn3 mutants, abnormal mitochondrial ultrastructure was observed, whereas chloroplast ultrastructure was not affected, implying that FPN3 plays a critical role in the mitochondria. Overall, our study suggests that FPN3 is essential for optimal iron homeostasis. Significance statementIron homeostasis must be tightly controlled in the mitochondria and chloroplasts, but iron trafficking in these organelles is not fully understood. Our work suggests that FPN3 is an iron exporter required for maintaining proper iron levels in mitochondria and chloroplasts. Furthermore, FPN3 is necessary for the optimal growth and normal mitochondrial ultrastructure under iron deficiency. This study reveals the physiological role of FPN3 and advances our understanding of iron regulation in mitochondria and chloroplasts.

plant biology↗

bioRxiv2019

YSL3-mediated copper distribution is required for fertility, grain yield, and size in Brachypodium.

Addressing the looming global food security crisis requires the development of high yielding crops. In this regard, the deficiency for the micronutrient copper in agricultural soils decreases grain yield and significantly impacts a globally important crop, wheat. In cereals, grain yield is determined by inflorescence architecture, flower fertility, grain size and weight. Whether copper is involved in these processes and how it is delivered to the reproductive organs is not well understood. We show that copper deficiency alters not only the grain set but also flower development in both wheat and its recognized model, Brachypodium distachyon, We then show that a brachypodium yellow-stripe-like 3 (YSL3) transporter localizes to the phloem and mediates copper delivery to flag leaves, anthers and pistils. Failure to deliver copper to these structures in the ysl3 CRISPR/Cas9 mutant results in delayed flowering, altered inflorescence architecture, reduced floret fertility, grain number, size, and weight. These defects are rescued by copper supplementation and are complemented by the YSL3 cDNA. This new knowledge will help to devise sustainable approaches for improving grain yield in regions where soil quality is a major obstacle for crop production.

plant biology↗