Differentially Expressed Genes Related to Flowering Transition between Once- and Continuous-Flowering Roses

PmRGL2/PmFRL3-PmSVP Module Regulates Flowering Time in Japanese apricot (Prunus mume Sieb. et Zucc.)

Temperate fruit trees rely on environmental and endogenous signals to trigger dormancy release and flowering. However, the knowledge of DELLA protein PmRGL2, a Prunus mume homolog of REPRESSOR OF GA-Like 2 (RGL2), which serves as an important inhibitory factor in gibberellin (gibberellin acid [GA]) signalling, is limited related to on its regulatory effects on dormancy release and flowering. In our study, the protein-protein interaction assays showed an interaction between PmRGL2 and PmFRL3, a Prunus mume homolog of FRIGIDA-LIKE (FRL). The FRL protein regulates flowering induction by binding to chaperone proteins. To understand the transcriptional regulation of PmRGL2 in Prunus mume, in detail's we constructed a ChIP-Seq library at four key stages of flower bud development. Genome-wide analysis screened a MCM1-AGAMOUSDEFICIENS Serum Response Factor box (MADS box) protein for two SHORT VEGETATIVE PHASEs (SVPs). Genetic analysis showed that overexpressing PmSVP in Arabidopsis thaliana reduced the GA content and delayed flowering, whereas PmSVP-like overexpression increased the GA content and promoted flowering. Protein-DNA binding assays revealed that the PmRGL2/PmFRL3 protein complex promoted PmSVP transcription while repressing PmSVP-like transcription, which inhibited the flowering process. As chilling requirements increased, the PmFRL3 protein was degraded. ThePmRGL2/PmFRL3 protein complex is disrupted. With the increase in the GA content within the flower buds, the PmRGL2 protein was degraded in response to GA signalling, and the function of PmSVP-like was released. It dominated flowering, leading to this process in Prunus mume. Therefore, we propose a mechanism by which the PmRGL2/PmFRL3 protein complex responds to GA and low-temperature signalling to regulate PmSVP and PmSVP-like synergistically and thus Prunus mume flowering time.

Genome-Wide Identification and Characterization of the GRAS Gene Family in Lettuce Revealed That Silencing LsGRAS13 Delayed Bolting

Lettuce is susceptible to high-temperature stress during cultivation, leading to bolting and affecting yield. Plant-specific transcription factors, known as GRAS proteins, play a crucial role in regulating plant growth, development, and abiotic stress responses. In this study, the entire lettuce LsGRAS gene family was identified. The results show that 59 LsGRAS genes are unevenly distributed across the nine chromosomes. Additionally, all LsGRAS proteins showed 100% nuclear localization based on the predicted subcellular localization and were phylogenetically classified into nine conserved subfamilies. To investigate the expression profiles of these genes in lettuce, we analyzed the transcription levels of all 59 LsGRAS genes in the publicly available RNA-seq data under the high-temperature treatment conducted in the presence of exogenous melatonin. The findings indicate that the transcript levels of the LsGRAS13 gene were higher on days 6, 9, 15, 18, and 27 under the high-temperature (35/30 °C) treatment with melatonin than on the same treatment days without melatonin. The functional studies demonstrate that silencing LsGRAS13 accelerated bolting in lettuce. Furthermore, the paraffin sectioning results showed that flower bud differentiation in LsGRAS13-silenced plants occurred significantly faster than in control plants. In this study, the LsGRAS genes were annotated and analyzed, and the expression pattern of the LsGRAS gene following melatonin treatment under high-temperature conditions was explored. This exploration provides valuable information and identifies candidate genes associated with the response mechanism of lettuce plants high-temperature stress.

Transcriptome Analysis of Lycoris chinensis Bulbs Reveals Flowering in the Age-Mediated Pathway

Lycoris is a summer bulbous flower that commonly needs to go through a long period of vegetative growth for 3 to 5 years before flowering. Plant flowering is regulated by a complex genetic network. Compared with most perennial flowers, knowledge on the molecular mechanism responsible for floral transition in bulbous flowers is lacking, and only a few genes that regulate flowering have been identified with few reports on the floral transition in Lycoris. In this study, we identified many differentially expressed genes (DEGs) and transcription factors (TFs) by RNA-Seq in L. chinensis bulbs of different ages, including one- to four-year-old nonflowering bulbs and four-year-old flowering bulbs. Some DEGs were enriched in Gene Ontology (GO) terms between the three- and four-year-old bulbs, and there most genes were enriched in terms of metabolic process and catalytic activity. In the four-year old bulbs, most of the DEGs that may be involved in flowering were classified under the GO term biological process, which was a totally different result from the vegetative bulbs. Some DEGs between flowering and nonflowering bulbs were enriched in plant hormone signal transduction, including the hormones auxin, cytokinin, abscisic acid, and ethylene, but no DEGs were enriched in the gibberellin pathway. Auxin is the main endogenous phytohormone involved in bulb growth and development, but cytokinin, abscisic acid, and ethylene were shown to increase in flowering bulbs. In addition, energy-metabolism-related genes maintain a high expression level in large bulbs, and some positive regulators (SPL, COL, and AP1) and early flowering genes were also shown to be highly expressed in the meristems of flowering bulbs. It suggested that sugar molecules may be the energy source that regulates the signal transduction of flowering by connecting with phytohormone signaling in Lycoris. A total of 1911 TFs were identified and classified into 89 categories, where the top six families with the largest gene numbers were C2H2, NAC, AP2/ERF-ERF, C3H, MYB-related, and WRKY. Most DEGs were in the AP2/ERF-ERF family, and most of them were downregulated in 4-year-old flowering bulbs. A number of families were reported to be involved in plant flowering, including NAC, AP2/ERF, MYB, WRKY, bZIP, MADS, and NF-Y. These results can act as a genetic resource to aid in the explanation of the genetic mechanism responsible for the flowering of Lycoris and other bulbous flowers.