Flowering in Persian walnut: patterns of gene expression during flower development

Abstract

Background: Flower development and sufficient fruit set are important parameters with respect to walnut yield. Knowledge about flowering genes of fruit trees can help to conduct better molecular breeding programs. Therefore, this study was carried out to investigate the expression pattern of some flowering genes (FT, SOC1, CAL, LFY and TFL1) in Persian walnut (cv. Chandler) during the growing season and winter dormancy. Results: The results showed that walnut flower induction and initiation in Shahmirzad, Iran occurred in early June and late September, respectively. After meeting chilling and heat requirement, flower differentiation and anthesis occurred in late-March and mid-April to early-May, respectively. Study of flowering gene expression showed that the expression of the FT gene increased in three stages including before breaking of bud dormancy, from late March to late April (coincided with flower differentiation and anthesis) and from late May to mid-June (coincided with flower induction). Like FT, the expression of SOC1 gene increased during flower induction and initiation (mid-May to early-August) as well as flower anthesis (mid-April to early-May). LFY and CAL genes as floral meristem identity genes are activated by FT and SOC1 genes. In contrast with flowering stimulus genes, TFL1 showed overexpression during winter dormancy which prevented flowering. Conclusion: The expression of FT gene activated downstream floral meristem identity genes including SOC1, CAL and LFY which consequently led to release bud dormancy as well as flower anthesis and induction. Also, TFL1 as a flowering inhibitor gene in walnut showed overexpression during the bud dormancy. Chilling accumulation reduced TFL1 gene expression and increased the expression of flowering genes which ultimately led to overcome dormancy.

Identification and Comparative Analysis of Genes and MicroRNAs Involved in the Floral Transition of the Xinjiang Early-Flowering Walnut (Juglans regia L.)

“…Currently, in walnut varieties, very little is known about the signals that underlie the transition between the juvenile and adult phases. Recent studies have identified flowering-related genes associated with this transition in walnut trees [21,22]. Remarkably, transcriptome profiling (RNA-seq) has revealed thirty-one DEGs associated with this floral transition in J. regia [22].…”

“…Compared with other plants, the mechanism of floral transition in walnut remains less studied. Using RNA sequencing (RNA-Seq) analyses, recent studies have proposed several candidate genes associated with the juvenile-adult phase change in walnut trees [21,22], but the critical genes regulating the precocious characteristic of EF walnut germplasm are still unknown. A high-quality chromosome-scale reference genome was recently released for the walnut [23].…”

Transcriptome profiling based on Illumina- and SMRT-based RNA-seq reveals circadian regulation of key pathways in flower bud development in walnut

“…De novo transcriptomes assemblies can be developed for the studies in functional genomics of plants. Mohammad Sadat-Hosseini [ 38 ] compared the assembled transcripts with transcripts of the walnut leaf, published genome assembly for the ‘Chandler’ cultivar using the BLAST algorithm and identified a number of novel homologue transcripts. This is a combine study of the full-length transcriptome sequences and transcriptome analysis to conduct the transcript detection of flower buds in walnut.…”

SPL9 mediates freezing tolerance by directly regulating the expression of CBF2 in Arabidopsis thaliana

“…Of them, some cold-induced genes are enriched in the responses to abiotic stresses; some cold-repressed genes are enriched in the regulation of transcription, and response to hormone stimulus [ 16 , 38 , 41 , 54 ]. In addition, some flowering genes, including FLOWERING LOCUS T ( FT ) and SUPPRESSOR OF OVEREXPRESSION OF CO 1 ( SOC1 ), are increased by cold to control flower development [ 21 , 39 ], indicating that some developmental genes function in cold response to balance the developmental processes under cold condition by interacting with cold-responsive genes.…”