A deficiency of the micronutrient copper (Cu) leads to infertility and grain/seed yield reduction in plants. How Cu affects fertility, which reproductive structures require Cu, and which transcriptional networks coordinate Cu delivery to reproductive organs is poorly understood. Using RNA-seq analysis, we showed that the expression of a gene encoding a novel transcription factor, CITF1 (Cu-DEFICIENCY INDUCED TRANSCRIPTION FACTOR1), was strongly upregulated in Arabidopsis thaliana flowers subjected to Cu deficiency. We demonstrated that CITF1 regulates Cu uptake into roots and delivery to flowers and is required for normal plant growth under Cu deficiency. CITF1 acts together with a master regulator of copper homeostasis, SPL7 (SQUAMOSA PROMOTER BINDING PROTEIN LIKE7), and the function of both is required for Cu delivery to anthers and pollen fertility. We also found that Cu deficiency upregulates the expression of jasmonic acid (JA) biosynthetic genes in flowers and increases endogenous JA accumulation in leaves. These effects are controlled in part by CITF1 and SPL7. Finally, we show that JA regulates CITF1 expression and that the JA biosynthetic mutant lacking the CITF1-and SPL7-regulated genes, LOX3 and LOX4, is sensitive to Cu deficiency. Together, our data show that CITF1 and SPL7 regulate Cu uptake and delivery to anthers, thereby influencing fertility, and highlight the relationship between Cu homeostasis, CITF1, SPL7, and the JA metabolic pathway.

Addressing the looming global food security crisis requires the development of high-yielding crops. In agricultural soils, deficiency in the micronutrient copper significantly decreases grain yield in wheat (Triticum aestivum), a globally important crop. 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 the Brachypodium yellow stripe-like 3 (YSL3) transporter localizes to the phloem, transports copper in frog (Xenopus laevis) oocytes, and facilitates copper delivery to reproductive organs and grains. Failure to deliver copper, but not iron, zinc, or manganese to these structures in the ysl3 CRISPR-Cas9 mutant results in delayed flowering, altered inflorescence architecture, reduced floret fertility, grain size, weight, and protein accumulation. These defects are rescued by copper supplementation and are complemented by YSL3 cDNA. This knowledge will help to devise sustainable approaches for improving grain yield in regions where soil quality is a major obstacle for crop production. Copper distribution by a phloem-localized transporter is essential for the transition to flowering, inflorescence architecture, floret fertility, size, weight, and protein accumulation in seeds.

Sulfur (S) is an essential macronutrient that has been proved to play an important role in regulating plant responses to various biotic and abiotic stresses. The present study was designed to investigate the effect of S status on polish wheat plant response to Mn toxicity. Results showed that Mn stress inhibited plant growth, disturbed photosynthesis and induced oxidative stress. In response to Mn stress, polish wheat plant activated several detoxification mechanisms to counteract Mn toxicity, including enhanced antioxidant defense system, increased Mn distribution in the cell wall and up-regulated genes involved in S assimilation. Moderate S application was found to alleviate Mn toxicity mainly by sequestering excess Mn into vacuoles, inhibiting Mn translocation from roots to shoots, stimulating activities of antioxidant enzymes and enhancing GSH production via up-regulating genes involved in S metabolism. However, application of high level S to Mn-stressed plants did not significantly alleviated Mn toxicity likely due to osmotic stress. In conclusion, moderate S application is beneficial to polish wheat plant against Mn toxicity, S exerts its effects via stimulating the antioxidant defense system and regulating the translocation and subcellular distribution of Mn, in which processes GSH plays an indispensable role.

The effects of exogenous salicylic acid (SA), sodium nitropusside (SNP, a nitric oxide donor), or their combination on dwarf polish wheat (Triticum polonicum L.) seedlings under UV-B stress were studied. UV-B stress significantly decreased plant height, shoot dry mass, pigment content, net photosynthetic rate, intercellular CO 2 concentration, stomatal conductance, transpiration rate, and variable to maximum chlorophyll fluorescence ratio (F v /F m ) in all plants, but less in the presence of SA, SNP, and their combination. On the other hand, there were considerable increases in malondialdehyde, proline, O 2•-and H 2 O 2 content under UV-B stress. When SA, SNP, and their combination were applied, the content of MDA, proline, H 2 O 2 , and O 2 •-was less increased. Moreover, there were considerable increases in activities of superoxide dismutase, peroxidase, ascorbate peroxidase, and glutathione reductase under UV-B stress and more in the presence of SA, SNP, and their combination. Therefore, it is considered that the combination of SA, SNP, and especially their combination can alleviate UV-B stress in dwarf polish wheat.

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35Addressing the looming global food security crisis requires the development of high yielding 36 crops. In this regard, the deficiency for the micronutrient copper in agricultural soils 37 decreases grain yield and significantly impacts a globally important crop, wheat. In cereals, 38 grain yield is determined by inflorescence architecture, flower fertility, grain size and weight. 39 Whether copper is involved in these processes and how it is delivered to the reproductive 40 organs is not well understood. We show that copper deficiency alters not only the grain set 41 but also flower development in both wheat and it's recognized model, Brachypodium 42 distachyon, We then show that a brachypodium yellow-stripe-like 3 (YSL3) transporter 43 localizes to the phloem and mediates copper delivery to flag leaves, anthers and pistils. 44 Failure to deliver copper to these structures in the ysl3 CRISPR/Cas9 mutant results in 45 delayed flowering, altered inflorescence architecture, reduced floret fertility, grain number, 46 size, and weight. These defects are rescued by copper supplementation and are complemented 47 by the YSL3 cDNA. This new knowledge will help to devise sustainable approaches for 48 improving grain yield in regions where soil quality is a major obstacle for crop production. 49 50Global food security and the demand for high-yielding grain crops are among the most urgent 51 drivers of modern plant sciences due to the current trend of population growth, extreme 52 weather conditions and decreasing arable land resources [1]. The grain yield is directly linked 53 to the crop and soil fertility. In this regard, it has been known for decades that the deficiency 54 for the micronutrient copper in alkaline, coarse-textured or organic soils that occupy more 55 than 30% of the world arable land, compromises crop fertility, reduces grain/seed yield and in 56 acute cases results in crop failure [2][3][4][5]. In accord with the essential role of copper in 57 reproduction, recent studies using synchrotron x-ray fluorescent (SXRF) microscopy 58 established that copper localizes to anthers and pistils of flowers in a model dicotyledonous 59 species, Arabidopsis thaliana, and failure to deliver copper to these reproductive organs 60 severely compromises fertility and seed set [6]. Although copper deficiency can be remedied 61 by the application of copper-based fertilizers, this approach is not environmentally friendly 62 and can lead to the build-up of toxic copper levels in soils [2,5,7]. Mineral nutrient 63 transporters have been recognized as key targets for improving the mineral use efficiency in 64 sustainable crop production [8]. Wheat is the world's third important staple crop after maize 65 (Zea mays) and rice (Oryza sativa); however, wheat grain yield remained relatively low under 66 marginal growing environments despite significant breeding efforts [9]. Wheat is also 67 regarded as the most sensitive to copper deficiency [2, 3,5]. How copper uptake and internal 68 transport is achieved in wheat and how it af...

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