Photoperiod and circadian controls play crucial roles in the regulation of chloroplast biogenesis. To understand more about the regulation of this process, we compared the greening of the first leaves of wild type barley and two WHIRLY1 (WHY1)-deficient lines. Seedlings were grown in darkness for 4 days prior and then exposed to light at the beginning of the photoperiod on the 5th day or under standard photoperiod conditions. The accumulation of chlorophyll, as well plastid-encoded photosynthetic transcripts and proteins was delayed in the WHY1-deficient lines under standard photoperiod conditions because of defects in plastid gene expression, ribosomal processing and photosynthetic protein accumulation. The acquisition of full photosynthetic capacity was delayed by about 11 days in the first leaves and the newly forming leaves of the WHY1-deficient lines compared to the wild type. However, the light-dependent accumulation of pigments, transcripts and photosynthetic proteins was similar in all lines when etiolated seedlings were exposed to light. These results demonstrate that WHY1 is required for the integration of photoperiod-dependent signalling and chloroplast development in barley leaves.

Atmospheric CO2 levels influences plant growth and susceptibility to pathogens and pests but there is little information on the mechanisms involved. We therefore studied how elevated atmospheric CO2 concentrations (eCO2) effects shoot branching and the performance of the pea aphid on wild type peas and on mutants that are defective in either strigolactone (SL) synthesis or signalling. Shoot branching and dry biomass accumulation were increased under eCO2 conditions in all lines. However, eCO2 decreased shoot water content only in the wild type peas but not in the SL mutants. Growth under eCO2 decreased the levels of salicylic acid and increased jasmonic acid in the wild type peas, without any significant effect on aphid fecundity. However, aphid numbers were increased on the SL mutants under both ambient and eCO2 conditions. Of the shoot phytohormones measured in this study, only gibberellic acid (GA3) was decreased in the SL mutants, an effect that was exacerbated by eCO2. There was a negative correlation between aphid fecundity and shoot GA3 levels. Taken together, these studies provide confirm that eCO2 modifies the levels of defence hormones and provides the first evidence that SL and GA3 are important regulators of plant responses to phloem-feeding insects.

Serious allergic reactions are increasing globally. Within this context, fatal anaphylaxis from hazelnut allergies is a critical public health concern. Hazelnuts, which are a common ingredient of many foods, contain many proteins that cause severe allergic reactions. Hazelnuts from all of the major commercial growing locations worldwide contained Spirosoma pollinicola sp proteins. This endotoxin-producing bacterium is linked to the allergenicity of hazelnut pollen. We were unable to remove the contamination by S. pollinicola proteins, showing that that this bacterium is a seed endosymbiont. Comparative proteomics revealed significant variations in the allergenic protein composition of nuts that correlated with patient immune responses. Hazelnuts from provenances 17 and 18 exhibited, lower levels of key antigens, particularly Cor a 9 and Cor a 14, highlighting their potential as candidates for genetic modification to mitigate allergenicity. Moreover, Spirosoma protein persistence may influence hazelnut allergenicity and the patient immune response.

Significant advances have been achieved in the biofortification of common beans to increase bioavailable Zinc (Zn) and iron (Fe) but the mechanisms involved remain poorly understood. We explored relationships between phosphate (Pi) nutrition and Zn and Fe accumulation in four bean genotypes (Edar, Nizok, Colorado and Chimbolos) that nominally show differences in seed Fe and Zn accumulation. Edar seeds had the lowest phytic acid-to-iron molar ratios, which is a measure of iron bioavailability, under full nutrient conditions. Phosphate limitation impaired plant metabolism and yield, decreasing seed Pi and phytate levels but with no effect on seed Fe and Zn accumulation. Edar plants had a higher seed yield under low Pi than the other lines. Analysis of the seed proteome also revealed that Edgar was highly resistant to Pi deficiency. The phytic acid-to-iron molar ratios in Edgar seeds under Pi deficiency was about twice that of low phytic acid ( lpa) beans that have a 90% lower phytic acid content compared to conventional beans. Proteome analysis revealed that primary metabolism is shifted in the lpa beans, particularly regarding carbohydrate metabolism. We conclude that the ability to maintain Pi cycling and transport pathways is important in controlling seed phytic acid-to-iron molar ratios.

The WHIRLY (WHY) DNA/RNA binding proteins fulfil multiple but poorly characterised functions in leaf development. WHY1 transcript levels were highest in the bases of 7-day old barley leaves. Immunogold labelling revealed that the WHY1 protein was more abundant in the nuclei than the proplastids of the leaf bases. Transcript and metabolite profiling analysis of barley lines (W1-1 and W1-7) lacking WHY1, which show delayed greening compared to the wild type. While the transcript profile of leaf development was largely unchanged in W1-1 and W1-7 leaves, there were differences in levels of several transcripts encoding transcription factors associated with chloroplast development. These include a barley homologue of the Arabidopsis GATA transcription factor that regulates stomatal development, greening and chloroplast development, NAC1, two transcripts with similarity to Arabidopsis GLK1 and two transcripts encoding ARF transcriptions factors with functions in leaf morphogenesis and development. Chloroplast proteins were less abundant in the W1-1 and W1-7 leaves than the wildtype. The levels of TCA cycle metabolites and GABA were significantly lower in WHY1 knockdown leaves than the wild type. We conclude that WHY1 functions in the nuclei of the cells in the leaf bases contributes to the regulation of chloroplast development.

Mechanisms that control of root system architecture are well characterised but little is known about how these processes respond to plant growth promoting rhizobacteria. We therefore studied how the presence of Pseudomonas oryzihabitans PGP01 altered wild type RSA and how these changes were modified in mutants that are defective antioxidant capacity (vtc2-1, vtc2-2, pad2-1, cad2-1 and rax1-1) or strigolactone (SL) synthesis (max3-9 and max4-1) or signalling (max2-3). The presence of P. oryzihabitans PGP01 decreased the length of primary and lateral roots but increased the number of lateral roots and lateral root density in the wild type roots but not in the SL mutants. The presence of synthetic SL, GR24 in combination with P. oryzihabitans PGP01 significantly decreased the number and length of lateral roots in the WT, max3-9 and max4-1 but not max2-3 seedlings. Lateral root density was increased in all genotypes in the presence of bacterium, but this effect was less pronounced in the ascorbate deficient vtc2-1 and vtc2-2 roots and absent from glutathione –deficient (pad2-1, cad2-1 and rax1-1) seedlings. Taken together, these results demonstrate the importance of SL-mediated signalling in root responses to growth promoting rhizobacteria, as well roles of cellular redox controls in these processes.