Characterization and expression analysis of the SPL gene family during floral development and abiotic stress in pecan (Carya illinoinensis)

SQUAMOSA promoter binding protein-like (SPL) genes are a type of plant-specific transcription factors that play crucial roles in the regulation of phase transition, floral transformation, fruit development, and various stresses. Although SPLs have been characterized in several model species, no systematic analysis has been studied in pecans, an important woody oil tree species. In this study, a total of 32 SPL genes (CiSPLs) were identified in the pecan genome. After conducting phylogenetic analysis of the conserved SBP proteins from Arabidopsis, rice, and poplar, the CiSPLs were separated into eight subgroups. The CiSPL genes within the same subgroup contained very similar exon-intron structures and conserved motifs. Nine segmentally duplicated gene pairs in the pecan genome and 16 collinear gene pairs between the CiSPL and AtSPL genes were identified. Cis-element analysis showed that CiSPL genes may regulate plant meristem differentiation and seed development, participate in various biological processes, and respond to plant hormones and environmental stresses. Therefore, we focused our study on the expression profiles of CiSPL genes during flower and fruit development. Most of the CiSPL genes were predominantly expressed in buds and/or female flowers. Additionally, quantitative real time PCR (qRT-PCR) analyses confirmed that CiSPL genes showed distinct spatiotemporal expression patterns in response to drought and salt treatments. The study provides foundation for the further exploration of the function and evolution of SPL genes in pecan.

Overexpression of SlMBP22 in Tomato Affects Flower Morphology, Fruit Set and Development

MADS-domain transcription factors have been clarified as key regulators involved in proper flower and fruit development in angiosperms. Bs genes, as members of the MADS-box subfamily, have been suggested to play an important role during the evolution of the reproductive organs in seed plants. Our knowledge about their effects on reproductive development in fruit crops like tomato (Solanum lycopersicum), however, is still unclear. Here, we found that the overexpression of SlMBP22 (SlMBP22-OE) resulted in considerable alterations regarding floral morphology, and affected the expression levels of several floral homeotic genes. Further analysis by yeast-two-hybrid assays demonstrated that SlMBP22 could form dimers with class A protein MACROCALYX (MC) and with SEPALLATA (SEP) floral homeotic proteins TM5 and TM29, respectively. In addition, pollen viability and cross-fertilization assays suggested that the defect in female reproductive development was responsible for infertility phenotype observed in the strong overexpression transgenic plants. The mild overexpression transgenic fruits were reduced in size, as a result of reduced cell expansion, rather than impaired cell division. Additionally, overexpression of SlMBP22 in tomato not only affected proanthocyanidin (PA) accumulation but also altered seed dormancy. Taken together, these findings may provide new insights into the knowledge of Bs MADS-box genes in flower and fruit development in tomato.

A gene expression atlas for kiwifruit (Actinidia chinensis) and network analysis of transcription factors

Background Transcriptomic studies combined with a well annotated genome have laid the foundations for new understanding of molecular processes. Tools which visualise gene expression patterns have further added to these resources. The manual annotation of the Actinidia chinensis (kiwifruit) genome has resulted in a high quality set of 33,044 genes. Here we investigate gene expression patterns in diverse tissues, visualised in an Electronic Fluorescent Pictograph (eFP) browser, to study the relationship of transcription factor (TF) expression using network analysis. Results Sixty-one samples covering diverse tissues at different developmental time points were selected for RNA-seq analysis and an eFP browser was generated to visualise this dataset. 2839 TFs representing 57 different classes were identified and named. Network analysis of the TF expression patterns separated TFs into 14 different modules. Two modules consisting of 237 TFs were correlated with floral bud and flower development, a further two modules containing 160 TFs were associated with fruit development and maturation. A single module of 480 TFs was associated with ethylene-induced fruit ripening. Three “hub” genes correlated with flower and fruit development consisted of a HAF-like gene central to gynoecium development, an ERF and a DOF gene. Maturing and ripening hub genes included a KNOX gene that was associated with seed maturation, and a GRAS-like TF. Conclusions This study provides an insight into the complexity of the transcriptional control of flower and fruit development, as well as providing a new resource to the plant community. The Actinidia eFP browser is provided in an accessible format that allows researchers to download and work internally.

Endogenous hormone causes flower and fruit drop of wax apple (Syzygium samarangense cv. Citra)

The aim of this study was to obtain information about the content of endogenous hormones that causes flowers and fruit drop of wax apple. The variables observed in the six stages of flower and fruit development that drop easily and retention of indole-­3-­acetic acid (IAA), cytokinin (zeatin and kinetin), gibberellins (GA3), 1­-amino cyclopropane­-1-­carboxylic acid (ACC), total sugar, and starch. Six stages of development of wax apple fruit: (1) Bud Development (initial flowering) 0­-3 days before anthesis. (2) Anthesis (perfect blooming flowers), 0­-7 days after anthesis. (3) Fruit set, 7­-14 days after anthesis. (4) Fruit development, 14-­28 days after anthesis. (5) Fruit Maturation, 28­-35 days after anthesis. (6) Fruit ripening, 35­-50 days after anthesis. The results showed that the content of IAA, zeatin, GA3, and total sugar of flowers and fruit of wax apple at 6 stages that would fall smaller than those of retention and ACC content and starch was higher in flower and fruits that drop easily than retention. The kinetin content in the flower development that drop easily is smaller than the retention but in the fruit development the kinetin content is not significantly different between those that drop easily and retention.

Silencing of the Ortholog of DEFECTIVE IN ANTHER DEHISCENCE 1 Gene in the Woody Perennial Jatropha curcas Alters Flower and Fruit Development

DEFECTIVE IN ANTHER DEHISCENCE 1 (DAD1), a phospholipase A1, utilizes galactolipids (18:3) to generate α-linolenic acid (ALA) in the initial step of jasmonic acid (JA) biosynthesis in Arabidopsis thaliana. In this study, we isolated the JcDAD1 gene, an ortholog of Arabidopsis DAD1 in Jatropha curcas, and found that it is mainly expressed in the stems, roots, and male flowers of Jatropha. JcDAD1-RNAi transgenic plants with low endogenous jasmonate levels in inflorescences exhibited more and larger flowers, as well as a few abortive female flowers, although anther and pollen development were normal. In addition, fruit number was increased and the seed size, weight, and oil contents were reduced in the transgenic Jatropha plants. These results indicate that JcDAD1 regulates the development of flowers and fruits through the JA biosynthesis pathway, but does not alter androecium development in Jatropha. These findings strengthen our understanding of the roles of JA and DAD1 in the regulation of floral development in woody perennial plants.

An Actinidia chinensis (kiwifruit) eFP browser and network analysis of transcription factors

BackgroundTranscriptomic studies combined with a well annotated genome have laid the foundations for new understanding of molecular processes. Tools which visualise gene expression patterns have further added to these resources. The manual annotation of the Actinidia chinensis (kiwifruit) genome has resulted in a high quality set of 33,044 genes. Here we investigate gene expression patterns in diverse tissues, visualised in an Electronic Fluorescent Pictograph (eFP) browser, to study the relationship of transcription factor (TF) expression using network analysis. ResultsSixty-one samples covering diverse tissues at different developmental time points were selected for RNAseq analysis and an eFP browser was generated to visualise this dataset. 2,839 TFs representing 57 different classes were identified and named. Network analysis of the TF expression patterns separated TFs into 14 different modules. Two modules consisting of 237 TFs were correlated with floral bud and flower development, a further two modules containing 160 TFs were associated with fruit development and maturation. A single module of 480 TFs was associated with ethylene-induced fruit ripening. Three “hub” genes correlated with flower and fruit development consisted of a HAF-like gene central to gynoecium development, an ERF and a DOF gene. Maturing and ripening hub genes included a KNOX gene that was associated with seed maturation, and a GRAS-like TF.ConclusionsThis study provides an insight into the complexity of the transcriptional control of flower and fruit development, as well as providing a new resource to the plant community. The eFP browser is provided in an accessible format that allows researchers to download and work internally.

Transcriptional Sequencing and Gene Expression Analysis of Various Genes in Fruit Development of Three Different Black Pepper (Piper nigrum L.) Varieties

Black pepper (Piper nigrum) is a vital spice crop with uses ranging from culinary to pharmacological applications. However, limited genetic information has constrained the understanding of the molecular regulation of flower and fruit development in black pepper. In this study, a comparison among three different black pepper varieties, Semengok Aman (SA), Kuching (KC), and Semengok 1 (S1), with varying fruit characteristics was used to provide insight on the genetic regulation of flower and fruit development. Next-generation sequencing (NGS) technology was used to determine the flower and fruit transcriptomes by sequencing on an Illumina HiSeq 2500 platform followed by de novo assembly using SOAPdenovo-Trans. The high-quality assembly of 66,906 of unigenes included 64.4% of gene sequences (43,115) with similarity to one or more protein sequences from the GenBank database. Annotation with Blast2Go assigned 37,377 genes to one or more Gene Ontology terms. Of these genes, 5,874 genes were further associated with the biological pathways recorded in the KEGG database. Comparison of flower and fruit transcriptome data from the three different black pepper varieties revealed a large number of DEGs between flower and fruit of the SA variety. Gene Ontology (GO) enrichment analysis further supports functions of DEGs between flower and fruit in the categories of carbohydrate metabolic processes, embryo development, and DNA metabolic processes while the DEGs in fruit relate to biosynthetic process, secondary metabolic process, and catabolic process. The enrichment of DEGs in KEGG pathways was also investigated, and a large number of genes were found to belong to the nucleotide metabolism and carbohydrate metabolism categories. Gene expression profiling of flower formation-related genes reveals that other than regulating the flowering in black pepper, the flowering genes might also be implicated in the fruit development process. Transcriptional analysis of sugar transporter and carbohydrate metabolism genes in different fruit varieties suggested that the carbohydrate metabolism in black pepper fruit is developmentally regulated, and some genes might serve as potential genes for future crop quality improvement. Study on the piperine-related gene expression analysis suggested that lysine-derived products might present in all stages of fruit development, but the transportation was only active at the early stage of fruit development. These results indicate several candidate genes related to the development of flower and fruit in black pepper and provide a resource for future functional analysis and potentially for future crop improvement.