Search

WHIRLY1 belongs to a family of plant-specific transcription factors capable of binding DNA or RNA in all three plant cell compartments that contain genetic materials. In Arabidopsis thaliana, WHIRLY1 has been studied at the later stages of plant development, including flowering and leaf senescence, as well as in biotic and abiotic stress responses. In this study, WHIRLY1 knockout mutants of A. thaliana were prepared by CRISPR/Cas9-mediated genome editing to investigate the role of WHIRLY1 during early seedling development. The loss-of-function of WHIRLY1 in 5-day-old seedlings did not cause differences in the phenotype and the photosynthetic performance of the emerging cotyledons compared with the wild type. Nevertheless, comparative RNA sequencing analysis revealed that the knockout of WHIRLY1 affected the expression of a small but specific set of genes during this critical phase of development. About 110 genes were found to be significantly deregulated in the knockout mutant, wherein several genes involved in the early steps of aliphatic glucosinolate (GSL) biosynthesis were suppressed compared with wild-type plants. The downregulation of these genes in WHIRLY1 knockout lines led to decreased GSL contents in seedlings and in seeds. Since GSL catabolism mediated by myrosinases was not altered during seed-to-seedling transition, the results suggest that AtWHIRLY1 plays a major role in modulation of aliphatic GSL biosynthesis during early seedling development. In addition, phylogenetic analysis revealed a coincidence between the evolution of methionine-derived aliphatic GSLs and the addition of a new WHIRLY in core families of the plant order Brassicales., (© 2024 The Author(s). The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

WHIRLY1 is a chloroplast-nucleus located DNA/RNA-binding protein with functions in development and stress tolerance. By overexpression of HvWHIRLY1 in barley, one line with a 10-fold and two lines with a 50-fold accumulation of the protein were obtained. In these lines, the relative abundance of the nuclear form exceeded that of the chloroplast form. Growth of the plants was shown to be compromised in a WHIRLY1 abundance-dependent manner. Over-accumulation of WHIRLY1 in chloroplasts had neither an evident impact on nucleoid morphology nor on the composition of the photosynthetic apparatus. Nevertheless, oeW1 plants were found to be compromised in the light reactions of photosynthesis as well as in carbon fixation. The reduction in growth and photosynthesis was shown to be accompanied by a decrease in the levels of cytokinins and an increase in the level of jasmonic acid. Gene expression analyses revealed that in nonstress conditions the oeW1 plants had enhanced levels of pathogen response (PR) gene expression indicating activation of constitutive defense. During growth in continuous light of high irradiance PR gene expression increased indicating that under stress conditions oeW1 are capable to further enhance defense., (© 2024 The Author(s). The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

Cereal grains contribute substantially to the human diet. The maternal plant provides the carbohydrate and nitrogen sources deposited in the endosperm, but the basis for their spatial allocation during the grain filling process is obscure. Here, vacuolar processing enzymes have been shown to both mediate programmed cell death (PCD) in the maternal tissues of a barley grain and influence the delivery of assimilate to the endosperm. The proposed centrality of PCD has implications for cereal crop improvement.

To survive under water deficiency, plants alter gene expression patterns, make structural and physiological adjustments, and optimize the use of water. Rapid degradation and turnover of proteins is required for effective nutrient recycling. Here, we examined the transcriptional responses of the C1A cysteine protease family to drought in barley and found that four genes were up-regulated in stressed plants. Knock-down lines for the protease-encoding genes HvPap-1 and HvPap-19 showed unexpected changes in leaf cuticle thickness and stomatal pore area. The efficiency of photosystem II and the total amount of proteins were almost unaltered in stressed transgenic plants while both parameters decreased in stressed wild-type plants. Although the patterns of proteolytic activities in the knock-down lines did not change, the amino acid accumulation increased in response to drought, concomitant with a higher ABA content. Whilst jasmonic acid (JA) and JA-Ile concentrations increased in stressed leaves of the wild-type and the HvPap-1 knock-down lines, their levels were lower in the HvPap-19 knock-down lines, suggesting the involvement of a specific hormone interaction in the process. Our data indicate that the changes in leaf cuticle thickness and stomatal pore area had advantageous effects on leaf defense against fungal infection and mite feeding mediated by Magnaporthe oryzae and Tetranychus urticae, respectively., (© The Author(s) 2018. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

WHIRLY1 in barley was isolated as a potential regulator of the senescence-associated gene HvS40. In order to investigate whether the plastid-nucleus-located DNA/RNA-binding protein WHIRLY1 plays a role in regulation of leaf senescence, primary foliage leaves from transgenic barley plants with an RNAi-mediated knockdown of the WHIRLY1 gene were characterized by typical senescence parameters, namely pigment contents, function and composition of the photosynthetic apparatus, as well as expression of selected genes known to be either down- or up-regulated during leaf senescence. When the plants were grown at low light intensity, senescence progression was similar between wild-type and RNAi-W1 plants. Likewise, dark-induced senescence of detached leaves was not affected by reduction of WHIRLY1. When plants were grown at high light intensity, however, senescence was induced prematurely in wild-type plants but was delayed in RNAi-W1 plants. This result suggests that WHIRLY1 plays a role in light sensing and/or stress communication between chloroplasts and the nucleus., (© The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

A family of putative PECTIN ESTERASE INHIBITOR (PEI) genes, which were detected in the genomic region co-segregating with the resistance gene Rrs2 against scald caused by Rhynchosporium commune in barley, were characterized and tested for their possible involvement in mediating resistance to the pathogen by complementation and overexpression analysis. The sequences of the respective genes were derived from two BAC contigs originating from the susceptible cultivar 'Morex'. For the genes HvPEI2, HvPEI3, HvPEI4 and HvPEI6, specific haplotypes for 18 resistant and 23 susceptible cultivars were detected after PCR-amplification and haplotype-specific CAPS-markers were developed. None of the tested candidate genes HvPEI2, HvPEI3 and HvPEI4 alone conferred a high resistance level in transgenic over-expression plants, though an improvement of the resistance level was observed especially with OE-lines for gene HvPEI4. These results do not confirm but also do not exclude an involvement of the PEI gene family in the response to the pathogen. A candidate for the resistance gene Rrs2 could not be identified yet. It is possible that Rrs2 is a PEI gene or another type of gene which has not been detected in the susceptible cultivar 'Morex' or the full resistance reaction requires the presence of several PEI genes.

Barley (Hordeum vulgare) spikes are developmentally switched from two-rowed to six-rowed by a single recessive gene, six-rowed spike 1 (vrs1), which encodes a homeodomain-leucine zipper I class transcription factor. Vrs1 is a paralog of HvHox2 and both were generated by duplication of an ancestral gene. HvHox2 is conserved among cereals, whereas Vrs1 acquired its current function during the evolution of barley. It was unclear whether divergence of expression pattern or protein function accounted for the functionalization of Vrs1. Here, we conducted a comparative analysis of protein functions and gene expression between HvHox2 and Vrs1 to clarify the functionalization mechanism. We revealed that the transcriptional activation activity of HvHOX2 and VRS1 was conserved. In situ hybridization analysis showed that HvHox2 is localized in vascular bundles in developing spikes, whereas Vrs1 is expressed exclusively in the pistil, lemma, palea and lodicule of lateral spikelets. The transcript abundance of Vrs1 was > 10-fold greater than that of HvHox2 during the pistil developmental stage, suggesting that the essential function of Vrs1 is to inhibit gynoecial development. We demonstrated the quantitative function of Vrs1 using RNAi transgenic plants and Vrs1 expression variants. Expression analysis of six-rowed spike mutants that are nonallelic to vrs1 showed that Vrs1 expression was up-regulated by Vrs4, whereas HvHox2 expression was not. These data demonstrate that the divergence of gene expression pattern contributed to the neofunctionalization of Vrs1., (© 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.)

Plant respiratory burst oxidase homologs are prominent sources of reactive oxygen species (ROS) in signal transduction and in interaction with microbes. However, the function of respiratory burst oxidase homologue (RBOH) genes in interaction with microbes might differ for certain plant and pathogen species. We produced transgenic barley knock down (KD) for the HvRBOHF2 isoform of NADPH oxidases. Young HvRBOHF2 KD shoots did not show obvious morphological alterations from the wild type but adult HvRBOHF2 KD plants developed fewer tillers, were less fertile, and showed spontaneous cell death in leaf mesophyll. Additionally, HvRBOHF2 KD plants were unable to contain wound-induced cell death. Before developmental failure became obvious, young HvRBOHF2 KD seedlings were much more susceptible to penetration by the biotrophic powdery mildew fungus Blumeria graminis f. sp. hordei. Strikingly, the B. graminis f. sp. hordei-induced cell-wall-associated oxidative burst was not substantially attenuated in HvRBOHF2 KD plants but enhanced susceptibility apparently influenced the subcellular site of hydrogen peroxide accumulation. Taken together, misexpression of HvRBOHF2 caused failure of barley to normally develop penetration resistance to B. graminis f. sp. hordei and to control leaf cell death.