The abscission regulatory module INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) / HAESA (HAE)-like receptor kinases in Solanaceae species: Functional analysis in Nicotiana benthamiana

[ES] La abscisión es un proceso de separación celular activo, organizado y altamente coordinado que permite el desprendimiento de órganos vegetativos y reproductivos completos, mediante la modificación de la adhesión celular y la desintegración de las paredes celulares en lugares específicos del cuerpo de la planta conocidos como zonas de abscisión. En Arabidopsis thaliana (Arabidopsis), la abscisión de órganos florales y hojas caulinares está regulada por la interacción entre el péptido hormonal (IDA), un par de proteínas quinasas de tipo receptor redundantes, (HAE y HSL2), y correceptores de la familia SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE. El conocimiento sobre la maquinaria molecular que regula la abscisión en especies de plantas de importancia económica de la familia de las solanáceas es en la actualidad escaso. En esta investigación de doctorado, se realizó un análisis funcional de los componentes del módulo de señalización de abscisión IDA-HAE en N. benthamiana. En la primera sección de este trabajo, se estudió el grado de conservación y la filogenia de las familias de genes IDA-like y HAE-like en especies relevantes del género Solanum, Capsicum y Nicotiana. Se analizó la expresión de estos genes en el alopoliploide N. benthamiana, con el fin de identificar miembros implicados en la abscisión y en la respuesta a condiciones de estrés abiótico como la sequía. En la segunda sección, se evaluó el efecto del silenciamiento y la sobreexpresión de NbenIDA1A y NbenIDA1B, dos homeólogos IDA-like de N. benthamiana que se asociaron con la abscisión de la corola en la sección anterior. Además, también se determinó el efecto sobre la abscisión de la corola del silenciamiento de NbenHAE.1. Las relaciones filogenéticas entre los miembros IDA-like de las solanáceas estudiadas, agruparon los dos pares de homeólogos de proteínas NbenIDA1 y NbenIDA2 con los prepropéptidos de Arabidopsis relacionados con la abscisión. El análisis de las regiones promotoras en busca de elementos reguladores reveló que estos dos pares de homeólogos contenían elementos de respuesta tanto hormonales como de respuesta a la sequía, aunque NbenIDA2A carecía de los elementos reguladores hormonales. Los análisis de expresión génica también indican que el par de homeólogos NbenIDA1 se regulan positivamente durante la abscisión de la corola. Los pares NbenIDA1 y NbenIDA2 mostraron una expresión diferencial tisular en condiciones de estrés hídrico, ya que los homeólogos NbenIDA1 se indujeron en hojas estresadas, mientras que los homeólogos NbenIDA2, especialmente NbenIDA2B, se indujeron en raíces estresadas. En las plantas con crecimiento activo no estresadas, los nudos y los entrenudos fueron los tejidos con los niveles de expresión más altos de todos los miembros de la familia IDA-like y sus receptores HAE-like putativos. El silenciamiento basado en VIGS del par de homeólogos NibenIDA1 y NbenHAE.1 suprimió la abscisión de la corola en flores de N. benthamiana, lo que fue causado por un bloqueo en la desintegración de la pared celular en la base de la corola, probablemente debido a la falta de inducción de las enzimas hidrolíticas relacionadas con la abscisión. La sobreexpresión ectópica del homeólogo NbenIDA1A adelantó la senescencia y la abscisión de la corola y afectó negativamente al crecimiento de las plantas de N. benthamiana. Los resultados obtenidos utilizando la aproximación VIGS mostraron que el par de homeólogos NbenIDA1 y el receptor NbenHAE.1, posiblemente actuando como un módulo de señalización similar al descrito en Arabidopsis, regulan la abscisión de la corola en las flores de N. benthamiana. Este es, por tanto, el primer ejemplo en una especie vegetal distinta de Arabidopsis thaliana que indica que el módulo de señalización de abscisión IDA-HAE/HSL2 se conserva en las angiospermas.[CA] L'abscisió és un procés de separació cel·lular actiu, organitzat i altament coordinat que permet el despreniment d'òrgans vegetatius i reproductius complets, mitjançant la modificació de l'adhesió cel·lular i la desintegració de les parets cel·lulars en llocs específics del cos de la planta coneguts com a zones d'abscisió. En Arabidopsis thaliana (Arabidopsis), l'abscisió d'òrgans florals i fulles caulinars està regulada per la interacció entre el pèptid hormonal (IDA), un parell de proteïnes cinases de tipus receptor redundants, (HAE i HSL2), i coreceptors de la família SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE. El coneixement sobre la maquinària molecular que regula l'abscisió en espècies de plantes d'importància econòmica de la família de les solanàcies és en l'actualitat escàs. En aquesta recerca de doctorat, es va realitzar una anàlisi funcional dels components del mòdul de senyalització d'abscisió IDA-HAE en N. benthamiana. A la primera secció d'aquest treball, es va estudiar el grau de conservació i la filogènia de les famílies de gens IDA-like i HAE-like en espècies rellevants de l'gènere Solanum, Capsicum i Nicotiana. Es va analitzar l'expressió d'aquests gens en l'al·lopoliploide N. benthamiana, per tal d'identificar membres implicats en l'abscisió i en la resposta a condicions d'estrès abiòtic, com la sequera. A la segona secció, es va avaluar l'efecte del silenciament i la sobreexpressió de NbenIDA1A i NbenIDA1B, dos homeòlegs IDA-like de N. benthamiana, que es van associar amb l'abscisió de la corol·la en la secció anterior. A més, també es va determinar l'efecte sobre l'abscisió de la corol·la del silenciament de NbenHAE.1. Les relacions filogenètiques entre els membres IDA-like de les solanàcies estudiades, van agrupar els dos parells d'homeòlegs de proteïnes NbenIDA1 i NbenIDA2 amb els prepropèptids d'Arabidopsis relacionats amb l'abscisió. L'anàlisi de les regions promotores a la recerca d'elements reguladors va revelar que aquests dos parells d'homeòlegs contenien elements de resposta tant hormonals com de resposta a la sequera, encara que NbenIDA2A mancava dels elements reguladors hormonals. Les anàlisis d'expressió gènica també indiquen que el parell d'homeòlegs NbenIDA1 es regulen positivament durant l'abscisió de la corol·la. Els parells NbenIDA1 i NbenIDA2 van mostrar una expressió diferencial tissular en condicions d'estrès hídric, ja que els homeòlegs NbenIDA1 es van induir en fulls estressades, mentre que els homeòlegs NbenIDA2, especialment NbenIDA2B, es van induir en arrels estressades. A les plantes amb creixement actiu no estressades, els nusos i els entrenusos van ser els teixits amb els nivells d'expressió més alts de tots els membres de la família IDA-like i els seus receptors HAE-like putatius. El silenciament basat en VIGS del parell d'homeòlegs NibenIDA1 i NbenHAE.1 va suprimir l'abscisió de la corol·la en flors de N. benthamiana, lo qual va ser causat per un bloqueig en la desintegració de la paret cel·lular a la base de la corol·la, probablement degut a la manca d'inducció dels enzims hidrolítics relacionades amb l'abscisió. La sobreexpressió ectòpica de l'homeòleg NbenIDA1A va avançar la senescència i l'abscisió de la corol·la i va afectar negativament el creixement de les plantes de N. benthamiana. Els resultats obtinguts utilitzant l'aproximació VIGS van mostrar que el parell d'homeòlegs NbenIDA1 i el receptor NbenHAE.1, possiblement actuant com un mòdul de senyalització similar al descrit en Arabidopsis, regulen l'abscisió de la corol·la en les flors de N. benthamiana. Aquest és, per tant, el primer exemple en una espècie vegetal diferent d'Arabidopsis thaliana que indica que el mòdul de senyalització d'abscisió IDA-HAE/HSL2 es conserva en les angiospermes.[EN] Abscission is an active, organized and highly coordinated cell separation process that enables the detachment of entire vegetative and reproductive organs, through the modification of cell-to-cell adhesion and breakdown of cell walls at specific sites on the plant body, known as abscission zones. In Arabidopsis thaliana (Arabidopsis), abscission of floral organs and cauline leaves is regulated by the interaction of the hormonal peptide (IDA), a pair of redundant receptorlike protein kinases, (HAE and HSL2), and SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE co-receptors. Knowledge about the molecular machinery regulating abscission in economically important plant species of the Solanaceae family is currently scarce. In this PhD research, a functional analysis of the components of the abscission signaling module IDA-HAE in N. benthamiana was carried out. In the first section of this work, the degree of conservation and the phylogeny of the IDA-like and HAE-like gene families in relevant species of the genus Solanum, Capsicumand Nicotiana were determined. The expression of these genes in the allopolyploid N. benthamiana was analyzed, in order to identify members involved in abscission and in the response to abiotic stress conditions, such as drought. In the second section, the effect of the silencing and overexpression of NbenIDA1A and NbenIDA1B, two N. benthamiana IDA-like homeologs, which were associated with corolla abscission in the previous section, was evaluated. Furthermore, the effect on corolla abscission of the silencing of NbenHAE.1 was also determined. The phylogenetic relationships among the IDA-like members of the Solanaceae studied, grouped the two pairs of NbenIDA1 and NbenIDA2 protein homeologs with the Arabidopsis prepropeptides related to abscission. Analysis of promoter regions searching for regulatory elements showed that these two pairs of homeologs contained both hormonal and drought response elements, although NbenIDA2A lacked the hormonal regulatory elements. Gene expression analyses also indicate that the pair of NbenIDA1 homeologs are upregulated during corolla abscission. NbenIDA1 and NbenIDA2 pairs showed tissue differential expression under water stress conditions, since NbenIDA1 homeologs were highly expressed in stressed leaves, while NbenIDA2 homeologs, especially NbenIDA2B, were highly expressed in stressed roots. In non-stressed active growing plants, nodes and internodes were the tissues with the highest expression levels of all members of the IDA-like family and their putative HAE-like receptors. VIGS-based silencing of the pair of NibenIDA1 homeologs and NbenHAE.1 suppressed corolla abscission in flowers of N. benthamiana, which was supported by a blockage in cell wall disassembly at the corolla base, probably due to the lack of upregulation of abscission-related hydrolytic enzymes. Ectopic over-expression of the homeolog NbenIDA1A advanced the timing of both corolla senescence and abscission and negatively affected the growth of N. benthamiana plants. The results obtained using the VIGS approach showed that the pair of NbenIDA1 homeologs and the NbenHAE.1 receptor, possibly acting as a signaling module similar to that described in Arabidopsis, regulate corolla abscission in N. benthamiana flowers. This is therefore the first example in a plant species other than Arabidopsis thaliana that indicates that the IDA-HAE/HSL2 abscission signaling module is conserved in angiosperms.Ventimilla Llora, D. (2021). The abscission regulatory module INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) / HAESA (HAE)-like receptor kinases in Solanaceae species: Functional analysis in Nicotiana benthamiana [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/167777TESI

Gibberellins Regulate Ovule Integument Development by Interfering with the Transcription Factor ATS

[EN] Gibberellins (GAs) are plant hormones that regulate most plant life cycle aspects, including flowering and fruit development. Here, we demonstrate the implication of GAs in ovule development. DELLA proteins, negative GA response regulators, act as positive factors for ovule integument development in a mechanism that involves transcription factor ABERRANT TESTA SHAPE (ATS). The seeds of the della global mutant, a complete loss-of-function of DELLA, and the ats-1 mutant are remarkably similar, with a round shape, a disorganized testa, and viviparism. These defects are the result of an alteration in integuments that fail to fully develop and are shorter than in wild-type plants. ats-1 also shows some GA-related phenotypes, for example, higher germination rates and early flowering. In fact, ats-1 has elevated GA levels due to the activation of GA biosynthesis genes, which indicates that ATS inhibits GA biosynthesis. Moreover, DELLAs and ATS proteins interact, which suggests the formation of a transcriptional complex that regulates the expression of genes involved in integument growth. Therefore, the repression of GA biosynthesis by ATS would result in the stabilization of DELLAs to ensure correct ATS-DELLA complex formation. The requirement of both activities to coordinate proper ovule development strongly argues that the ATS-DELLA complex acts as a key molecular factor. This work provides the first evidence for a role of GAs in ovule and seed development.This work was supported by grants BIO2011-26302 and BIO2014-55946 from the Spanish Ministry of Science and Innovation and the Spanish Ministry of Economy and Competitiveness, respectively, and ACOMP/2013/048 and ACOMP/2014/106 from the Generalitat Valenciana to M.A.P.-A. R.S. received a PhD fellowship from the Spanish Ministry of Science and Innovation.Gómez Jiménez, MD.; Ventimilla-Llora, D.; Sacristán Tarrazó, R.; Perez Amador, MA. (2016). Gibberellins Regulate Ovule Integument Development by Interfering with the Transcription Factor ATS. Plant Physiology. 172(4):2403-2415. doi:10.1104/pp.16.01231S24032415172

An RNA-Seq-based reference transcriptome for Citrus

Previous RNA-Seq studies in citrus have been focused on physiological processes relevant to fruit quality and productivity of the major species, especially sweet orange. Less attention has been paid to vegetative or reproductive tissues, while most Citrus species have never been analysed. In this work, we characterized the transcriptome of vegetative and reproductive tissues from 12 Citrus species from all main phylogenetic groups. Our aims were to acquire a complete view of the citrus transcriptome landscape, to improve previous functional annotations and to obtain genetic markers associated with genes of agronomic interest. 28 samples were used for RNA-Seq analysis, obtained from 12 Citrus species: C.medica, C.aurantifolia, C.limon, C.bergamia, C.clementina, C.deliciosa, C.reshni, C.maxima, C.paradisi, C.aurantium, C.sinensis and Poncirus trifoliata. Four different organs were analysed: root, phloem, leaf and flower. A total of 3421 million Illumina reads were produced and mapped against the reference C.clementina genome sequence. Transcript discovery pipeline revealed 3326 new genes, the number of genes with alternative splicing was increased to 19739, and a total of 73797 transcripts were identified. Differential expression studies between the four tissues showed that gene expression is overall related to the physiological function of the specific organs above any other variable. Variants discovery analysis revealed the presence of indels and SNPs in genes associated with fruit quality and productivity. Pivotal pathways in citrus such as those of flavonoids, flavonols, ethylene and auxin were also analysed in detail

Transcriptomic analysis of Citrus clementina mandarin fruits maturation reveals a MADS-box transcription factor that might be involved in the regulation of earliness

Background: Harvest time is a relevant economic trait in citrus, and selection of cultivars with different fruit maturity periods has a remarkable impact in the market share. Generation of early- and late-maturing cultivars is an important target for citrus breeders, therefore, generation of knowledge regarding the genetic mechanisms controlling the ripening process and causing the early and late phenotypes is crucial. In this work we analyze the evolution of the transcriptome during fruit ripening in 3 sport mutations derived from the Fina clementine (Citrus clementina) mandarin: Clemenules (CLE), Arrufatina (ARR) and Hernandina (HER) that differ in their harvesting periods. CLE is considered a mid-season cultivar while ARR and HER are early- and late-ripening mutants, respectively. Results: We used RNA-Seq technology to carry out a time course analysis of the transcriptome of the 3 mutations along the ripening period. The results indicated that in these mutants, earliness and lateness during fruit ripening correlated with the advancement or delay in the expression of a set of genes that may be implicated in the maturation process. A detailed analysis of the transcription factors known to be involved in the regulation of fruit ripening identified a member of the MADS box family whose expression was lower in ARR, the early-ripening mutant, and higher in HER, the late-ripening mutant. The pattern of expression of this gene during the maturation period was basically contrary to those of the ethylene biosynthetic genes, SAM and ACC synthases and ACC oxidase. The gene was present in hemizygous dose in the early-ripening mutant. Conclusions: Our analysis provides new clues about the genetic control of fruit ripening in citrus and allowed the identification of a transcription factor that could be involved in the early phenotype.Financial support was provided by the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, INIA, (Ministerio de Economía, Industria y Competitividad e Innovación, Spain) trough grant # RTA-00071-C06–01

Identificación de interactores de Dellas en los pistilos y frutos de Arabidopsis thaliana

[EN] DELLAs are intracellular repressors of gibberellin response. In this study, we sought to identify and characterize interactors of DELLA proteins involved in controlling the development of pistil and fruit of Arabidopsis, to understand the molecular mechanism by which the GAs promote the growth of these tissues.[ES] as DELLAs son represores de la respuesta a giberelinas. En este trabajo hemos tratado de identificar y caracterizar proteínas interactoras de las proteínas DELLA implicadas en el control del desarrollo del pistilo y fruto de Arabidopsis, para conocer el mecanismo molecular por el cual las GAs favorecen el crecimiento de estos tejidos.Ventimilla Llora, D. (2015). Identificación de interactores de Dellas en los pistilos y frutos de Arabidopsis thaliana. http://hdl.handle.net/10251/75587Archivo delegad

Gibberellins Regulate Ovule Integument Development by Interfering with the Transcription Factor ATS

Gibberellins (GAs) are plant hormones that regulate most plant life cycle aspects, including flowering and fruit development. Here, we demonstrate the implication of GAs in ovule development. DELLA proteins, negative GA response regulators, act as positive factors for ovule integument development in a mechanism that involves transcription factor ABERRANT TESTA SHAPE (ATS). The seeds of the della global mutant, a complete loss-of-function of DELLA, and the ats-1 mutant are remarkably similar, with a round shape, a disorganized testa, and viviparism. These defects are the result of an alteration in integuments that fail to fully develop and are shorter than in wild-type plants. ats-1 also shows some GA-related phenotypes, for example, higher germination rates and early flowering. In fact, ats-1 has elevated GA levels due to the activation of GA biosynthesis genes, which indicates that ATS inhibits GA biosynthesis. Moreover, DELLAs and ATS proteins interact, which suggests the formation of a transcriptional complex that regulates the expression of genes involved in integument growth. Therefore, the repression of GA biosynthesis by ATS would result in the stabilization of DELLAs to ensure correct ATS-DELLA complex formation. The requirement of both activities to coordinate proper ovule development strongly argues that the ATS-DELLA complex acts as a key molecular factor. This work provides the first evidence for a role of GAs in ovule and seed development

IDA (INFLORESCENCE DEFICIENT IN ABSCISSION)-like peptides and HAE (HAESA)-like receptors regulate corolla abscission in Nicotiana benthamiana flowers

Background: Abscission is an active, organized, and highly coordinated cell separation process enabling the detachment of aerial organs through the modification of cell-to-cell adhesion and breakdown of cell walls at specific sites on the plant body known as abscission zones. In Arabidopsis thaliana, abscission of floral organs and cauline leaves is regulated by the interaction of the hormonal peptide INFLORESCENCE DEFICIENT IN ABSCISSION (IDA), a pair of redundant receptor-like protein kinases, HAESA (HAE) and HAESA-LIKE2 (HSL2), and SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) co-receptors. However, the functionality of this abscission signaling module has not yet been demonstrated in other plant species. Results: The expression of the pair of NbenIDA1 homeologs and the receptor NbenHAE.1 was supressed at the base of the corolla tube by the inoculation of two virus-induced gene silencing (VIGS) constructs in Nicotiana benthamiana. These gene suppression events arrested corolla abscission but did not produce any obvious effect on plant growth. VIGS plants retained a higher number of corollas attached to the flowers than control plants, an observation related to a greater corolla breakstrength. The arrest of corolla abscission was associated with the preservation of the parenchyma tissue at the base of the corolla tube that, in contrast, was virtually collapsed in normal corollas. In contrast, the inoculation of a viral vector construct that increased the expression of NbenIDA1A at the base of the corolla tube negatively affected the growth of the inoculated plants accelerating the timing of both corolla senescence and abscission. However, the heterologous ectopic overexpression of citrus CitIDA3 and Arabidopsis AtIDA in N. benthamiana did not alter the standard plant phenotype suggesting that the proteolytic processing machinery was unable to yield active peptides. Conclusion: Here, we demonstrate that the pair of NbenIDA1 homeologs encoding small peptides of the IDA-like family and the receptor NbenHAE.1 control cellular breakdown at the base of the corolla tube awhere an adventitious AZ should be formed and, therefore, corolla abscission in N. benthamiana flowers. Altogether, our results provide the first evidence supporting the notion that the IDA-HAE/HSL2 signaling module is conserved in angiosperms