SlTPL1 Silencing Induces Facultative Parthenocarpy in Tomato

Abstract

Facultative parthenocarpy is of great practical value. However, the molecular mechanism underlying facultative parthenocarpy remains elusive. Transcriptional co-repressors (TPL) act as a central regulatory hub controlling all nine phytohormone pathways. Previously, we proved that SlTPLs participate in the auxin signaling pathway by interacting with auxin/indole acetic acid (Aux/IAAs) in tomato; however, their function in fruit development has not been studied. In addition to their high expression levels during flower development, the interaction between SlTPL1 and SlIAA9 stimulated the investigation of its functional significance via RNA interference (RNAi) technology, whereby the translation of a protein is prevented by selective degradation of its encoded mRNA. Down-regulation of SlTPL1 resulted in facultative parthenocarpy. Plants of SlTPL1-RNAi transgenic lines produced similar fruits which did not show any pleiotropic effects under normal conditions. However, they produced seedless fruits upon emasculation and under heat stress conditions. Furthermore, SlTPL1-RNAi flower buds contained higher levels of cytokinins and lower levels of abscisic acid. To reveal how SlTPL1 regulates facultative parthenocarpy, RNA-seq was performed to identify genes regulated by SlTPL1 in ovaries before and after fruit set. The results showed that down-regulation of SlTPL1 resulted in reduced expression levels of cytokinin metabolism-related genes, and all transcription factors such as MYB, CDF, and ERFs. Conversely, down-regulation of SlTPL1 induced the expression of genes related to cell wall and cytoskeleton organization. These data provide novel insights into the molecular mechanism of facultative tomato parthenocarpy and identify SlTPL1 as a key factor regulating these processes.

Genome-wide identification and characterization of parthenocarpic fruit set-related gene homologs in cucumber (Cucumis sativus L.)

“…Based on bibliomic data, 35 PRGs were identified from various crops including tomato ( Solanum lycopersicum ) , Arabidopsis thaliana, fig ( Ficus cracia ) , common pear ( Pyrus communis ) , grape ( Vitis vinifera ) and loquat ( Eriobotrya japonica ) (Table S1 ). The genes included SlDELLA (negative regulator of GA signalling) 27 , SlARFs (activation/inhibition of auxin responsive genes) 18 , 24 , SlAGAMOUS/AGL (MADS family transcription factor) 28 , 29 , SlTPL (Transducing family protein/WD40 repeat family protein) 30 , SlPAT (Synthesis of active gibberellic acid- natural parthenocarpy) 28 , 31 , EjYUCCA (for indole-3-pyruvate monooxygenase in auxin biosynthesis) 32 , FcPYR (ABA signalling pathway) 8 , 33 , FcGID1 ( Gibberellin Insensitive Dwarf1— gibberellic acid receptor) 34 , 35 , , VvPISTILLATA/DEFICIENS (MADS family transcription factors- controls petal and stamen floral organ identity) 10 , 36 , 37 , CsLOG (Lonely Guy enzyme- conversion of nucleotide precursors into active forms) 8 , 38 , CsCKX (Cytokinin oxidase- cytokinin degradation) 8 , 38 , CsIPT (Adenylateisopentenylatetransferase-cytokinin biosynthesis) 8 , 32 , CsWD40 (WD-40 repeat family protein- cytokinin responses) 24 , CsCYP735A (for Cytochrome P450 monooxygenase- cytokinin biosynthesis) 8 , 38 AtFIE (Fertilization Independent Endosperm) 10 , 22 , AtFIS (Fertilization Independent Seed) 10 , 20 , AtMEDEA (Polycomb group protein- transcriptional repression) 21 , 39 , AtMET1 (methyl transferase- methylation of symmetric CpG residues) 39 , and PbGA2ox (Gibberellic acid oxidase) 40 . The gDNA sequences of them were used as queries to identify homologous genes in the cucumber genome (9930v2.0, https://cucurbitgenomics.org/ ), which are listed in Table…”

“…We reviewed the literature and identified PRGs from various fruit or vegetable crops that are either directly or indirectly involved in regulation of parthenocarpy. The crop plants included Cucumis sativus L. (cucumber) 8 , 24 , 26 , Solanum lycopersicum L. (tomato) 30 , 74 , 81 – 84 , Pyrus communis L . (pear) 44 , 85 , 86 , Ficus carica L. (fig) 33 , 87 ; and across various other taxa 10 , 21 , 32 , 39 , 47 , 88 .…”

“…We reviewed the literature and identified PRGs from various fruit or vegetable crops that are either directly or indirectly involved in regulation of parthenocarpy. The crop plants included Cucumis sativus L. (cucumber) 8,24,26 , Solanum lycopersicum L. (tomato) 30,74,[81][82][83][84] , Pyrus communis L. (pear) 44,85,86 , Ficus carica L. (fig) 33,87 ; and across various other taxa 10,21,32,39,47,88 . Genomic DNA sequences of those PRGs in the cucumber genome were obtained through BLASTn in several databases Ensembl Plants, Cucurbits Genome Database and NCBI , which were further cross-verified by using BLASTp with default settings (expected threshold 0.05) and percentage identity more than 80% and e-value less than zero on query sequences using Ensembl Plant database (https:// plants.…”

Characterization of yield and fruit quality parameters of Vietnamese elite tomato lines generated through phenotypic selection and conventional breeding methods

“…There are parthenocarpy cultivars – which were reported to carry pat-2 alleles or a novel pat-k gene – that have been used as breeding materials in Japan (Gorguet et al, 2008; Takisawa et al, 2017). Parthenocarpy mutant alleles of SlTPL1 and IAA9 regulate seed phenotype via controlling the metabolism of phytohormones such as auxin, cytokinins, and abscisic acid (Wang et al 2009; Mazzucato et al 2015; He et al 2021). These alleles were generated by gene modification via RNAi or CRISPR/Cas9-mediated gene editing.…”

Expression of a maize SOC1 gene enhances soybean yield potential through modulating plant growth and flowering

“…Modulating expression of MADS-box genes have a potential to increase crop yield 34 – 36 . For example, increasing the expression of a homolog of the Arabidopsis FUL / AGL8 gene of maize ( ZMM28 ) enhanced maize grain yield in the field 37 .…”