Ethylene-induced differential gene expression during abscission of citrus leaves

Abstract

The main objective of this work was to identify and classify genes involved in the process of leaf abscission in Clementina de Nules (Citrus clementina Hort. Ex Tan.). A 7 K unigene citrus cDNA microarray containing 12 K spots was used to characterize the transcriptome of the ethylene-induced abscission process in laminar abscission zone-enriched tissues and the petiole of debladed leaf explants. In these conditions, ethylene induced 100% leaf explant abscission in 72 h while, in air-treated samples, the abscission period started later and took 240 h. Gene expression monitored during the first 36 h of ethylene treatment showed that out of the 12 672 cDNA microarray probes, ethylene differentially induced 725 probes distributed as follows: 216 (29.8%) probes in the laminar abscission zone and 509 (70.2%) in the petiole. Functional MIPS classification and manual annotation of differentially expressed genes highlighted key processes regulating the activation and progress of the cell separation that brings about abscission. These included cell-wall modification, lipid transport, protein biosynthesis and degradation, and differential activation of signal transduction and transcription control pathways. Expression data associated with the petiole indicated the occurrence of a double defensive strategy mediated by the activation of a biochemical programme including scavenging ROS, defence and PR genes, and a physical response mostly based on lignin biosynthesis and deposition. This work identifies new genes probably involved in the onset and development of the leaf abscission process and suggests a different but co-ordinated and complementary role for the laminar abscission zone and the petiole during the process of abscission.

Induction and Characterization of Fruit Abscission during Early Physiological Fruit Drop in Citrus

“…These results indicate that a similar mechanism regulates abscission for both detached fruits in agar medium and attached fruits on the tree. Detached leaf explant incubation has also been performed to investigate the leaf abscission process in citrus (Agustí et al, 2008). We conclude that incubation of detached fruits in agar medium is a useful method for inducing fruit abscission.…”

ABA-deficiency and molecular mechanisms involved in the dehydration response and ripening of citrus fruit

“…In agreement, Gómez-Cadenas et al (1996; pointed out the key role of ethylene as activator of leaf abscission in waterstressed citrus trees, and suggested that ABA was the primary stress signal responsible for the increase in ethylene. Work performed in citrus fruit further revealed a crosstalk between ABA and ethylene for triggering fruit abscission (Gómez-Cadenas et al, 2000;Agustí et al, 2008). Results obtained in mature sweet cherry, which are very prone to abscission, suggested, however, that the ABA increase observed at late stages of fruit ripening was more likely related to Introduction ethylene in the development and ripening of climacteric fruits, such as nectarine and tomato, is well known (Ziliotto et al, 2008;Zhang et al, 2009b) since several reports suggested that the ABA accumulation just before the peak of ethylene production triggers ethylene biosynthesis responsible for climacteric fruit ripening (Zhang et al, 2001;Zhang et al, 2009a;Bastías et al, 2011).…”

“…cDNA samples were Cy5-labelled and co-hybridized with a Cy3-labelled cDNA reference pool from a mixture containing equal amounts of RNA from all experimental samples assayed. The use of this reference sample has been widely used in Citrus transcriptomic research since it represents a powerful tool for reducing the number of hybridizations to make all the possible pairwise comparisons between samples (Agustí et al, 2008).…”

“…Citrus cDNA microarrays have been developed in this Consortium (Forment et al, 2005;Martínez-Godoy et al, 2008), and the latest generation contains 21081 (20K) putative citrus unigenes, which offers a good representation of the citrus genome. In the framework of the CFGP, important insights in citrus biology have been already achieved (Cercós et al, 2006;Gandía et al, 2007;Agustí et al, 2008;Alós et al, 2008;Huerta et al, 2008;Brumós et al, 2009;Ballester et al, 2011). Global changes in gene expression in response to drought have been characterized in citrus seedlings (Gimeno et al, 2009).…”

El virus del manchado foliar de los cítricos: caracterización del promotor del RNA subgenómico del gen de la proteína de la cápsida y del supresor del silenciamiento de RNA

“…Con estas colecciones de ESTs se ha elaborado una micromatriz que contiene 21081 unigenes (Martinez-Godoy et al, 2008) y que está siendo utilizada por distintos grupos de investigación para definir patrones de expresión génica en distintos tejidos, estadios del desarrollo del fruto (floración, fructificación, maduración) (Cercós et al, 2006;Alós et al, 2008) como respuesta a diversos tratamientos de estrés abiótico (salinidad, sequía, deficiencia en hierro, etc.) (Agustí et al, 2008;Huerta et al, 2008) o biótico (virus, hongos, etc. ) (Gandía et al, 2007) y para distinguir variedades .…”