Functional interconnections of HY1 with MYC2 and HY5 in Arabidopsis seedling development

Arabidopsis seedling development is controlled by many regulatory genes involved in multiple signaling pathways. The functional relationships of these genes working in multiple signaling cascades have started to be unraveled. Arabidopsis HY1/HO1 is a rate-limiting enzyme involved in biosynthesis of phytochrome chromophore. HY5 (a bZIP protein) promotes photomorphogenesis, however ZBF1/MYC2 (a bHLH protein) works as a negative regulator of photomorphogenic growth and light regulated gene expression. Further, MYC2 and HY1 have been shown to play important roles in jasmonic acid (JA) signaling pathways. Here, we show the genetic interactions of HY1 with two key transcription factor genes of light signaling, HY5 and MYC2, in Arabidopsis seedling development. Our studies reveal that although HY1 acts in an additive manner with HY5, it is epistatic to MYC2 in light-mediated seedling growth and gene expression. This study further demonstrates that HY1 additively or synergistically functions with HY5, however it works upstream to MYC2 in JA signaling pathways. Taken together, this study demonstrates the functional interrelations of HY1, MYC2 and HY5 in light and JA signaling pathways

An ectomycorrhizal fungus alters sensitivity to jasmonate, salicylate, gibberellin, and ethylene in host roots.

The phytohormones jasmonate, gibberellin, salicylate, and ethylene regulate an interconnected reprogramming network integrating root development with plant responses against microbes. The establishment of mutualistic ectomycorrhizal symbiosis requires the suppression of plant defense responses against fungi as well as the modification of root architecture and cortical cell wall properties. Here, we investigated the contribution of phytohormones and their crosstalk to the ontogenesis of ectomycorrhizae (ECM) between grey poplar (Populus tremula x alba) roots and the fungus Laccaria bicolor. To obtain the hormonal blueprint of developing ECM, we quantified the concentrations of jasmonates, gibberellins, and salicylate via liquid chromatography-tandem mass spectrometry. Subsequently, we assessed root architecture, mycorrhizal morphology, and gene expression levels (RNA sequencing) in phytohormone-treated poplar lateral roots in the presence or absence of L. bicolor. Salicylic acid accumulated in mid-stage ECM. Exogenous phytohormone treatment affected the fungal colonization rate and/or frequency of Hartig net formation. Colonized lateral roots displayed diminished responsiveness to jasmonate but regulated some genes, implicated in defense and cell wall remodelling, that were specifically differentially expressed after jasmonate treatment. Responses to salicylate, gibberellin, and ethylene were enhanced in ECM. The dynamics of phytohormone accumulation and response suggest that jasmonate, gibberellin, salicylate, and ethylene signalling play multifaceted roles in poplar L. bicolor ectomycorrhizal development

Coordination between zinc and phosphate homeostasis involves the transcription factor PHR1, the phosphate exporter PHO1, and its homologue PHO1;H3 in Arabidopsis

Phosphate over-accumulates in shoots in response to Zn deprivation. Results shown in this article suggest key roles of PHR1 and PHO1 and a counteractive function of PHO1;H3 in controlling root-to-shoot phosphate translocation in Arabidopsi

Abordagem fisiológica e molecular da capacidade de tolerância à secura de Jatropha curcas L.: uma planta resistente à seca

Tese de mestrado. Biologia (Biologia Humana e Ambiente). Universidade de Lisboa, Faculdade de Ciências, 2010A seca afecta as plantas, originando-lhes stress. Para o Homem, como as culturas agrículas fornecem 2/3 do alimento da população mundial, este problema pode provocar graves consequências do ponto de vista da saúde pública. As plantas desenvolveram mecanismos de resposta à secura, que podem ser regulados pela expressão de diversos genes, que permitem à planta adaptar-se a novas condições ambientais. A planta Jatropha curcas L. possui grande capacidade de adaptação a condições de seca, o que poderá dever-se a numerosos factores. Este trabalho teve como objectivo monitorizar alterações de expressão génica em genes já anteriormente correlacionados com a tolerância à seca, seja em Jatropha ou noutras plantas modelo, utilizando para o efeito duas linhas de J. curcas L.. Estas linhas são originárias de ambientes com regimes hídricos diferentes, seco versus tropical húmido. As alterações detectadas ao nível da expressão transcricional foram correlacionadas com ensaios morfo-fisiológicos efectuados nas duas variedades de J. curcas, com vista à caracterização do seu comportamento sob stress hídrico. Concluiu-se que as duas linhas de J. curcas L., sob stress hídrico, possuem uma resposta semelhante ao nível da expressão génica. Foi também possível verificar neste trabalho que as duas linhas de J. curcas L., submetidas ao mesmo stress, apresentam um comportamento morfo-fisiológico diferente. A linha de regime hídrico seco demonstra um ritmo de crescimento lento mas constante e um melhor aproveitamento da água disponível, em contraste com a linha de regime tropical húmido que mostra um crescimento rápido, interrompido por stress hídrico. Parece ainda haver alguma correlação entre a expressão de alguns genes e alterações morfológicas nas linhas de J. curcas L.. Os resultados obtidos apontam para eventuais estratégias diferentes entre as duas linhas de J. curcas L. relativamente à forma de lidar com o stress hídrico, embora os ensaios realizados não tenham permitido verificar uma expressão génica discriminante.Drought affects plants, causing stress. For mankind, to whom crops represent 2/3 of world food reserves, this problem can cause several issues related to human health. Plants have evolved mechanisms to cope with stress, which can be regulated through different genes, helping the plant in its adaptation to the new environmental conditions. Jatropha curcas L. is a plant that is able to survive in extreme drought environments, which may be due to a great number of causes. The goal of this work was to monitor gene expression changes from already known drought-responsive genes, in Jatropha or in other model plants. For this purpose, we used two lines of J. curcas L., which have their origin in two different hydrologic regimes (arid versus tropical). Gene expression changes were correlated to physiological and morphological tests under drought in the two J. curcas L. lines, in order to have new insights in how this plant species deal with drought. With this work, we could conclude that both lines under drought stress have a similar gene expression pattern. We could also conclude that the two J. curcas L. lines have a different physiological and morphological response under drought stress. The arid line shows a slow but constant growth rate and a good water usage. In the opposite direction, the tropical line shows to have a bigger growth rate, although it is impaired under drought. There seems to be a correlation between morphological and expressions of some genes in Jatropha curcas lines. Our results support an eventual different strategy among the ecotypes to cope with drought stress, although we could not observe a discriminating gene expression pattern

\u3ci\u3eWheat streak mosaic virus\u3c/i\u3e alters the transcriptome of its vector, wheat curl mite (\u3ci\u3eAceria tosichella Keifer\u3c/i\u3e), to enhance mite development and population expansion

Wheat streak mosaic virus (WSMV; genus Tritimovirus; family Potyviridae) is an economically important wheat virus that is transmitted by the wheat curl mite (WCM; Aceria tosichella Keifer) in a persistent manner. Virus–vector coevolution may potentially influence vector gene expression to prolong viral association and thus increase virus transmission efficiency and spread. To understand the transcriptomic responses of WCM to WSMV, RNA sequencing was performed to assemble and analyse transcriptomes of WSMV viruliferous and aviruliferous mites. Among 7291 de novo-assembled unigenes, 1020 were differentially expressed between viruliferous and aviruliferous WCMs using edgeR at a false discovery rate ≤0.05. Differentially expressed unigenes were enriched for 108 gene ontology terms, with the majority of the unigenes showing downregulation in viruliferous mites in comparison to only a few unigenes that were upregulated. Protein family and metabolic pathway enrichment analyses revealed that most downregulated unigenes encoded enzymes and proteins linked to stress response, immunity and development. Mechanistically, these predicted changes in mite physiology induced by viral association could be suggestive of pathways needed for promoting virus–vector interactions. Overall, our data suggest that transcriptional changes in viruliferous mites facilitate prolonged viral association and alter WCM development to expedite population expansion, both of which could enhance viral transmission

Wheat streak mosaic virus alters the transcriptome of its vector, wheat curl mite (Aceria tosichella Keifer), to enhance mite development and population expansion

Wheat streak mosaic virus (WSMV; genus Tritimovirus; family Potyviridae) is an economically important wheat virus that is transmitted by the wheat curl mite (WCM; Aceria tosichella Keifer) in a persistent manner. Virus–vector coevolution may potentially influence vector gene expression to prolong viral association and thus increase virus transmission efficiency and spread. To understand the transcriptomic responses of WCM to WSMV, RNA sequencing was performed to assemble and analyse transcriptomes of WSMV viruliferous and aviruliferous mites. Among 7291 de novo-assembled unigenes, 1020 were differentially expressed between viruliferous and aviruliferous WCMs using edgeR at a false discovery rate 0.05. Differentially expressed unigenes were enriched for 108 gene ontology terms, with the majority of the unigenes showing downregulation in viruliferous mites in comparison to only a few unigenes that were upregulated. Protein family and metabolic pathway enrichment analyses revealed that most downregulated unigenes encoded enzymes and proteins linked to stress response, immunity and development. Mechanistically, these predicted changes in mite physiology induced by viral association could be suggestive of pathways needed for promoting virus–vector interactions. Overall, our data suggest that transcriptional changes in viruliferous mites facilitate prolonged viral association and alter WCM development to expedite population expansion, both of which could enhance viral transmission

Association analysis of photoperiodic flowering time genes in west and central African sorghum [Sorghum bicolor (L.) Moench]

Abstract Background: Photoperiod-sensitive flowering is a key adaptive trait for sorghum (Sorghum bicolor) in West and Central Africa. In this study we performed an association analysis to investigate the effect of polymorphisms within the genes putatively related to variation in flowering time on photoperiod-sensitive flowering in sorghum. For this purpose a genetically characterized panel of 219 sorghum accessions from West and Central Africa was evaluated for their photoperiod response index (PRI) based on two sowing dates under field conditions. Results: Sorghum accessions used in our study were genotyped for single nucleotide polymorphisms (SNPs) in six genes putatively involved in the photoperiodic control of flowering time. Applying a mixed model approach and previously-determined population structure parameters to these candidate genes, we found significant associations between several SNPs with PRI for the genes CRYPTOCHROME 1 (CRY1-b1) and GIGANTEA (GI)