No abstract

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.

State of the art proton exchange membrane (PEM) fuel cells often use PtM (M= Co or Ni) as cathode catalysts and Ce-based additives in the membrane in order to enhance their performance and durability. During operation, however, these metals dissolve and cations transport from their initial positions, which decreases their efficacy and can cause fouling of ionomer regions, resulting in performance losses and local membrane failure. Here, we report the development of a confocal microprobe X-ray fluorescence technique to directly observe transient, µm-scale through-thickness migration of Ce3+ cations, in operando for the first time. At 80°C and 50% RH, Ce3+ migrates from the PEM into ionomer regions of the cathode catalyst layer (CL), saturating the CL ionomer and forming a gradient in the PEM after around 10 minutes at 100 mA cm-2. Upon removal of load, Ce3+ diffuses and equilibrates between ionomer regions of the CL and PEM. These results demonstrate the rapid effects of cation transport in the through-thickness direction over the range of current densities tested (50-100 mA cm-2).

No abstract

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...