Transcriptome Analysis of Tomato Flower Pedicel Tissues Reveals Abscission Zone-Specific Modulation of Key Meristem Activity Genes

Abstract

Tomato flower abscises at the anatomically distinct abscission zone that separates the pedicel into basal and apical portions. During abscission, cell separation occurs only at the abscission zone indicating distinctive molecular regulation in its cells. We conducted a transcriptome analysis of tomato pedicel tissues during ethylene promoted abscission. We found that the abscission zone was the most active site with the largest set of differentially expressed genes when compared with basal and apical portions. Gene Ontology analyses revealed enriched transcription regulation and hydrolase activities in the abscission zone. We also demonstrate coordinated responses of hormone and cell wall related genes. Besides, a number of ESTs representing homologs of key Arabidopsis shoot apical meristem activity genes were found to be preferentially expressed in the abscission zone, including WUSCHEL (WUS), KNAT6, LATERAL ORGAN BOUNDARIES DOMAIN PROTEIN 1(LBD1), and BELL-like homeodomain protein 1 (BLH1), as well as tomato axillary meristem genes BLIND (Bl) and LATERAL SUPPRESSOR (Ls). More interestingly, the homologs of WUS and the potential functional partner OVATE FAMILIY PROTEIN (OFP) were subsequently down regulated during abscission while Bl and AGL12 were continuously and specifically induced in the abscission zone. The expression patterns of meristem activity genes corroborate the idea that cells of the abscission zone confer meristem-like nature and coincide with the course of abscission and post-abscission cell differentiation. Our data therefore propose a possible regulatory scheme in tomato involving meristem genes that may be required not only for the abscission zone development, but also for abscission.

The ARF, AUX/IAA and GH3 gene families in citrus: genome-wide identification and expression analysis during fruitlet drop from abscission zone A

“…Abebie et al (2008) reported that the floret abscission in cestrum cut flower was associated with the expression level of AUX/IAA genes, which was consistent with the results reported by Meir et al (2010). Likewise, there are also several reports suggesting GH3 genes are involved in fruitlet or flower abscission (Kuang et al 2012;Wang et al 2013). The above-mentioned results suggested that the roles of GH3s, ARFs and AUX/IAAs in fruitlet abscission may considerably vary among plant species.…”

KNOX Protein OSH15 Induces Grain Shattering by Repressing Lignin Biosynthesis Genes

“…This set of cellular characteristics is reminiscent of meristematic tissues. Several genes involved in SAM maintenance and the initiation of axillary meristems are expressed in the AZ (Shi et al, 2011;Nakano et al, 2013;Wang et al, 2013). Therefore, it has been proposed that AZ cells have a meristematic identity.…”

Profiling gene expression in citrus fruit calyx abscission zone (AZ-C) treated with ethylene

“…The process includes four major steps: development of the AZ tissue, acquisition of competence to respond to abscission signals, activation of abscission following perception of abscission signals, and differentiation of a protective layer on the proximal side of the AZ (Patterson 2001). Extensively transcriptome analyses have been performed to investigate the gene expression changes during organs shedding among different plant species and in different AZs of leaves, fruits and flowers Agustí et al 2008;Cai and Lashbrook 2008;Meir et al 2010;Botton et al 2011;Nakano et al 2012Nakano et al , 2013Wang et al 2013). These studies revealed that the abscission-related genes are mostly involved in ethylene and auxin biosynthesis and signal transduction, cell wall modification, and various stress responses Agustí et al 2008;Cai and Lashbrook 2008;Meir et al 2010;Botton et al 2011;Nakano et al 2012Nakano et al , 2013Wang et al 2013).…”

“…Extensively transcriptome analyses have been performed to investigate the gene expression changes during organs shedding among different plant species and in different AZs of leaves, fruits and flowers Agustí et al 2008;Cai and Lashbrook 2008;Meir et al 2010;Botton et al 2011;Nakano et al 2012Nakano et al , 2013Wang et al 2013). These studies revealed that the abscission-related genes are mostly involved in ethylene and auxin biosynthesis and signal transduction, cell wall modification, and various stress responses Agustí et al 2008;Cai and Lashbrook 2008;Meir et al 2010;Botton et al 2011;Nakano et al 2012Nakano et al , 2013Wang et al 2013). Wang et al (2013) conducted a transcriptome analysis of tomato pedicel tissues during ethylene promoted abscission, and found that the abscission zone was the most active site with the largest set of differentially expressed genes when compared with basal and apical portions.…”

“…These studies revealed that the abscission-related genes are mostly involved in ethylene and auxin biosynthesis and signal transduction, cell wall modification, and various stress responses Agustí et al 2008;Cai and Lashbrook 2008;Meir et al 2010;Botton et al 2011;Nakano et al 2012Nakano et al , 2013Wang et al 2013). Wang et al (2013) conducted a transcriptome analysis of tomato pedicel tissues during ethylene promoted abscission, and found that the abscission zone was the most active site with the largest set of differentially expressed genes when compared with basal and apical portions. Nakano et al (2013) profiled genome-wide gene expression in tomato flower pedicels at the pre-abscission stage, and found that region-specific transcriptional regulators and genes for auxin activity may prevent flower abscission in the absence of signal or establish competence to respond to the abscission signal.…”