Long-day Conditions Research Articles

A Series of Novel Alleles of Ehd2 Modulating Heading and Salt Tolerance in Rice.

Rice (Oryza sativa L.) is a staple crop for nearly half of the global population and one of China's most extensively cultivated cereals. Heading date, a critical agronomic trait, determines the regional and seasonal adaptability of rice varieties. In this study, a series of mutants (elh5 to elh12) exhibiting extremely late heading under both long-day (LD) and short-day (SD) conditions were identified from an ethyl methanesulfonate (EMS) mutant library. Using MutMap and map-based cloning, the causative gene was identified as a novel allele of Ehd2/OsID1/RID1/Ghd10. Functional validation through CRISPR/Cas9 knockout and complementation assays confirmed its role in regulating heading. The elh6 mutation was found to cause intron retention due to alternative splicing. Ehd2 encodes a Cys-2/His-2-type zinc finger transcription factor with an IDD domain and transcriptional activity in yeast. Its expression peaks in developing leaves before heading and spikes during reproductive conversion. In elh6 mutants, delayed heading resulted from downregulating the Ehd1-Hd3a pathway genes. Salinity stress significantly hampers rice growth and productivity. Transcriptomic analysis of elh10 and ZH8015 seedlings exposed to salt stress for 24 h identified 5150 differentially expressed genes (DEGs) at the seedling stage, predominantly linked to stress response pathways. Ehd2 was revealed as a modulator of salt tolerance, likely through the regulation of ion transport, enzyme activity, and antioxidant systems. This study establishes Ehd2 as a pivotal factor in promoting heading while negatively regulating salt tolerance in rice.

Photoperiodic plasticity of pigment-dispersing factor immunoreactive fibers projecting toward prothoracicotropic hormone neurons in flesh fly Sarcophaga similis larvae.

Larvae of the flesh fly, Sarcophaga similis exhibit photoperiodic responses to control pupal diapause. Although the external coincidence model is applicable to S. similis photoperiodism, it remains unknown how the circadian clock system integrates day-length information. To explore the mechanisms, we examined the neural circuitry involving circadian clock lateral neurons (LNs) and prothoracicotropic hormone (PTTH) neurons. We also examined the photoperiodic effects on LN-fiber patterns in third-instar S. similis larvae. Immunohistochemistry showed that the clock protein PERIOD and the neuropeptide pigment-dispersing factor (PDF) were co-localized in four cells per brain hemisphere, and we named these PDF-LNs of S. similis. Single-cell polymerase chain reaction of backfilled neurons from the ring gland showed that two pairs of pars lateralis neurons with contralateral axons (PL-c neurons) to the ring gland expressed ptth. Double labeling with immunohistochemistry and backfills revealed that PDF-immunoreactive varicose fibers projected close to fibers from PL-c neurons. short neuropeptide f (snpf) receptor and glutamate-gated chloride channel but not pdf receptor were expressed in PL-c neurons. sNPF and L-glutamate but not PDF acutely inhibited the spontaneous firing activity of PL-c neurons. The number of PDF-immunoreactive varicosities of PDF-LNs in the dorsal protocerebrum was significantly higher under short-day than that under long-day conditions in a time-dependent manner. These results suggest that sNPF and/or glutamate signaling to PTTH neurons and PDF-LNs form a potential neural circuity for the photoperiodic control of pupal diapause and that photoperiod modifies the connectivity strength between PDF-LNs and their post- or pre-neurons in the circuitry.

Co-profiling of single-cell gene expression and chromatin landscapes in stickleback pituitary

The pituitary gland is a key endocrine gland with various physiological functions including metabolism, growth, and reproduction. It comprises several distinct cell populations that release multiple polypeptide hormones. Although the major endocrine cell types are conserved across taxa, the regulatory mechanisms of gene expression and chromatin organization in specific cell types remain poorly understood. Here, we performed simultaneous profiling of the transcriptome and chromatin landscapes in the pituitary cells of the three-spined stickleback (Gasterosteus aculeatus), which represents a good model for investigating the genetic mechanisms underlying adaptive evolution. We obtained pairwise gene expression and chromatin profiles for 5184 cells under short- and long-day conditions. Using three independent clustering analyses, we identified 16 distinct cell clusters and validated their consistency. These results advance our understanding of the regulatory dynamics in the pituitary gland and provide a reference for future research on comparative physiology and evolutionary biology.

OsBBX2 Delays Flowering by Repressing Hd3a Expression Under Long-Day Conditions in Rice

Members of the B-Box (BBX) family of proteins play crucial roles in the growth and development of rice. Here, we identified a rice BBX protein, Oryza sativa BBX2 (OsBBX2), which exhibits the highest expression in the root. The transcription of OsBBX2 follows a diurnal rhythm under photoperiodic conditions, peaking at dawn. Functional analysis revealed that OsBBX2 possesses transcriptional repression activity. The BBX2 was overexpressed in the rice japonica cultivar Longjing 11 (LJ11), in which Ghd7 and PRR37 were non-functional or exhibited weak functionality. The overexpression of OsBBX2 (OsBBX2 OE) resulted in a delayed heading date under a long-day (LD) condition, whereas the bbx2 mutant exhibited flowering patterns similar to the wild type (WT). Additionally, transcripts of Ehd1, Hd3a, and RFT1 were downregulated in the OsBBX2 OE lines under the LD condition. OsBBX2 interacted with Hd1 (BBX18), and the bbx2 hd1 double mutant displayed a late flowering phenotype comparable to that of hd1. Furthermore, OsBBX2 enhanced the transcriptional repression of Hd3a through its interaction with Hd1, as demonstrated in the protoplast-based assay. Taken together, these findings suggest that the OsBBX2 delays flowering by interacting with Hd1 and co-repressing Hd3a transcription.

Flowering Characteristics and Expression Patterns of Key Genes in Response to Photoperiod in Different Chrysanthemum Varieties

Chrysanthemum × morifolium Ramat. is a globally renowned ornamental flower. It includes numerous varieties, most of which are typical short-day (SD) plants, and the flowering characteristics of different chrysanthemum varieties in response to the photoperiod vary greatly. In this study, seven representative chrysanthemum varieties were selected for a comparative analysis of flowering traits under long-day conditions (16 h/8 h day/night) and short-day conditions (12 h/12 h day/night). It was found that three varieties (‘A44’, ‘C60’, and ‘183’) belonged to obligatory short-day varieties and four varieties (‘A20’, ‘C1’, ‘C27’, and ‘C31’) belonged to facultative short-day varieties. The short-day conditions not only induced earlier flowering but also improved flowering quality in the facultative SD varieties. Different chrysanthemum varieties required different light conditions to complete the vegetative stage and reach the floral competent state. Seven chrysanthemum varieties, ‘A44’, ‘C60’, ‘183’, ‘A20’, ‘C1’, ‘C27’, and ‘C31’, reached a floral competent state in the L20, L20, L22, L22, L18, L20, and L24 periods, respectively, and were most sensitive to SD induction at this time. The expression patterns of key floral genes in the photoperiod pathway were analyzed and it was found that CmCRY1, CmCRY2, CmGI1, CmGI2, and CmCO were mainly expressed in leaves. Then, comparing the expression levels of these genes under LD and SD conditions, the expression of CmGI1, CmGI2, CmCO, and CmFTL were not significantly induced in the obligatory SD varieties, while the expression of them in the facultative SD varieties were induced by SD conditions. This may be the reason why the facultative varieties could respond to SD conditions more quickly to complete the floral transition. In addition, SD induction under different photoperiodic conditions and growth states resulted in differences in the phenotype of flowering. This result provides guidance for the artificial regulation of chrysanthemum flowering and improvement of ornamental quality, as well as clues for analyzing the flowering mechanism of chrysanthemums under different photoperiod conditions.

The role of sugar transporter BrSWEET11 in promoting plant early flowering and preliminary exploration of its molecular mechanism.

BrSWEET11 accelerated Arabidopsis thaliana flowering, while silencing Brsweet11 in Brassica rapa delayed flowering relative to controls. BrSWEET11 is involved in sucrose transport after being induced by long-day conditions. SWEETs (Sugars Will Eventually Be Exported Transporters) are sugar outflow transporters that may participate in the regulation of plant flowering. In this study, the open reading frame of Brassica rapa ssp. pekinensis SWEET11 (BrSWEET11) was cloned and found to be 858bp in length and encode 285 amino acids, which is typical of SWEET family proteins. The BrSWEET11 gene was strongly expressed in reproductive growth organs, particularly flowers, according to tissue expression analyses and GUS histochemical staining. BrSWEET11 promotes early flowering in Arabidopsis thaliana by 3-4days, whereas Brsweet11 silencing in Brassica rapa delays flowering by 8-12days relative to controls. BrSWEET11 promoted early flowering in A. thaliana, and compared with that in control plants, flowering was delayed in Brsweet11-silenced Brassica rapa. Transcriptome analysis of BrSWEET11-overexpressing A. thaliana and wild-type (WT) plants was performed and the results showed that eight key flowering genes jointly regulated flowering time, which was also validated in the Brsweet11-silenced plants. In addition, through photoperiod treatments and sugar content measurements, it was found that the expression of BrSWEET11 is induced by long-day conditions and is involved in sucrose transport. Further investigation using yeast library screening, yeast two-hybrid, and bimolecular fluorescence complementation assay techniques revealed that the BrSWEET11 protein interacts with the sugar transporter 4a (BrSUT4a) protein. Therefore, BrSWEET11 was induced by long-day conditions, and may promote early flowering in Brassica rapa through sucrose transport. This study provides a theoretical basis for elucidating the molecular mechanism through which SWEET genes are involved in flowering time regulation in Brassica rapa.

Safflower CtFT genes orchestrating flowering time and flavonoid biosynthesis

BackgroundSafflower thrives in dry environments but faces difficulties with flowering in wet and rainy summers. Flavonoids play a role in flower development and can potentially alleviate these challenges. Furthermore, the FLOWERING LOCUS T (FT) family of phosphatidylethanolamine-binding protein (PEBP) genes play a crucial role in the photoperiodic flowering pathway. However, their direct impact on flowering and flavonoid biosynthesis under different light duration is elusive.ResultsUtilizing the genome sequencing of Safflower (Jihong NO.1), the current study identifies three specific genes (CtFT1, CtFT2, and CtFT3) that exhibit upregulation in response to long-day conditions. The overexpression of CtFT2, displayed an early, whereas CtFT1 and CtFT3 late flowering phenotype in Arabidopsis thaliana. Interestingly, the transient overexpression of CtFT1 in safflower leaves caused early flowering, while overexpressing CtFT2 and CtFT3 led to late flowering. Additionally, overexpressing CtFT3 in Arabidopsis and CtFT1, CtFT2, and CtFT3 in safflower leaves, significantly increased flavonoid synthesis.ConclusionsThese findings showed that overexpression of CtFT genes could affect the flowering time and significantly increase the flavonoid content of safflower. The function of CtFT gene is different in safflower and Arabidopsis. This study provides valuable insights into the role of CtFT genes in flower formation and flavonoid synthesis in safflower, which may help in improving safflower breeding quality and its adaptability to diverse environmental conditions.

Genome-Wide Identification and Expression Analysis of Pseudo-Response Regulators (PRRs) in the Tea Plant Camellia sinensis (L.) O. Kuntze

The circadian clock plays a vital role in facilitating plant adaptation to rhythmically changing environmental factors. Pseudo-response regulators (PRRs) are key components regulating the plant circadian clock and have been extensively characterized in model plants. However, the PRRs in the tea plant have not been comprehensively studied. In this study, seven CsPRRs were cloned from the tea plant. Domain, phylogenetic evolution, gene structure, motifs, and cis-acting element analysis revealed their sequence characters and suggested that the first subgroup members, CsPRR1a, 1b, 5a, 5b, 7, and 37, may be responsible for circadian rhythm regulation and abiotic stress responses, while the second subgroup member, CsPRR2, may be involved in development and chloroplast function regulation. Most CsPRRs showed relatively higher expression in flowers, implying their potential roles in photoperiod-regulated flower induction. Moreover, rhythmic expression of CsPRR7, 5b, 5a, 37, 1b, and 1a was observed under long-day conditions in a sequential manner. Additionally, CsPRRs were differently induced/inhibited by cold, heat, and drought stresses in tissue-specific and photoperiod-related manners. A stronger cold induction of CsPRRs was observed under long-day conditions than under short-day conditions. And, among the two tested tissues, changes in the expression of CsPRRs caused by various stresses were more obvious in young shoots. Studies using a floriferous cultivar (FDDB) and an oliganthous cultivar (PYTZ) implied that CsPRRs also played crucial roles in tea-plant flower induction. This study presents the first comprehensive analysis of CsPRRs in the tea plant, providing vital information for further elucidation of CsPRR functions. It also suggests that tissue type and photoperiod conditions should be taken into consideration when conducting gene function studies in the tea plant.

Transcription factors BnaC09.FUL and BnaC06.WIP2 antagonistically regulate flowering time under long-day conditions in Brassica napus.

Appropriate flowering time in rapeseed (Brassica napus L.) is vital for preventing losses from weather, diseases, and pests. However, the molecular basis of its regulation remains largely unknown. Here, a genome-wide association study identifies BnaC09.FUL, a MADS-box transcription factor, as a promising candidate gene regulating flowering time in B. napus. BnaC09.FUL expression increases sharply in B. napus shoot apices near bolting. BnaC09.FUL overexpression results in early flowering, while BnaFUL mutation causes delayed flowering in B. napus. A zinc finger transcription factor, BnaC06.WIP2, is identified as an interaction partner of BnaC09.FUL, and BnaC06.WIP2 overexpression delays flowering in B. napus, with RNA sequencing revealing its influence on the expression of many flowering-associated genes. We further demonstrate that BnaC06.WIP2 directly represses the expression of BnaA05.SOC1, BnaC03.SOC1, BnaC04.SOC1, BnaC06.FT, BnaA06.LFY, BnaC07.FUL, BnaA08.CAL, and BnaC03.CAL and indirectly inhibits the expression of other flowering time-related genes. Genetic and molecular investigations highlight the antagonistic relationship between BnaC09.FUL and BnaC06.WIP2 in regulating the flowering time in B. napus through direct regulation of the expression of BnaC03.SOC1, BnaA08.CAL, and BnaC03.CAL. Overall, our findings provide a mechanism by which the BnaC09.FUL-BnaC06.WIP2 transcriptional regulatory module controls the flowering time in B. napus.

A single-base deletion in exon 2 of Hd1 delineates monogenic recessive photoperiod insensitivity in aromatic Joha rice: a novel allele for seasonal adaptability

BackgroundAssam's aromatic Joha rice is a unique rice class famous for its aroma, taste, and nutritional benefits, which fetch high market prices in domestic and international markets. Joha landraces are inherently poor yielders due to their strong aroma and predominantly photoperiod sensitivity. Hybridization involving non-aromatic HYVs improves yield with concomitant loss of quality. In this context, mutation breeding, a sustainable approach where genetic mutations are induced to create desirable traits, often provides useful allelic variation in specific morpho-agronomic traits. The present study delves into the genetic characterization of a photoperiod-insensitive mutant. As part of our mutation breeding programme, this mutant was isolated from a gamma ray-induced M2 population of a Joha rice landrace, Kon Joha.ResultsThe mutant was unique, and a single recessive gene conditions the induced photoperiod insensitivity. Mutant gene tagging involved 402 SSR and InDel markers, and later polymorphic markers were used for bulk segregant analysis (BSA) in the F2 population of ‘mutant × Kalijeera (distant parent)’. BSA revealed an association between the SSR marker RM527 and this mutant trait. This marker is present on chromosome 6 of the rice genome. Using chromosome 6-specific SSR markers in polymorphic screening and BSA revealed another associated marker, RM19725, for the mutant trait. The genomic interval between RM527 and RM19725 harbors a photoperiod-insensitive gene, Hd1, on chromosome 6. Cloning and sequencing of Hd1 genomic fragments from the parents and mutants revealed a single-base deletion in exon 2, leading to a frameshift mutation in the Hd1 protein. This mutation in exon 2 leads to severe structural abnormalities in the CCT domain of the Hd1 protein that is critical for the interaction of the repressing complex with conserved response elements in the florigen gene under long-day conditions, thereby causing photoperiod insensitivity.ConclusionsThe mutant's pleasant aroma and other quality characteristics, comparable to those of the parent cultivar, hold significant promise. They expand its potential use in a structured breeding programme aimed at developing high-value aromatic Joha rice. This rice, resilient to winter- and summer-growing environments and with broad seasonal adaptability, could revolutionize the rice market. The practical value of our research is underscored by this exciting possibility.

Juvenile hormone regulates reproductive diapause through both canonical and noncanonical pathways in the bean bug Riptortus pedestris

Diapause is an adaptive developmental arrest commonly utilized by animals to cope with seasonal changes. Central to this process are hormonal events that bridge photoperiodic cues and physiological changes. In insect reproductive diapause, the absence of juvenile hormone (JH) serves as the primary endocrine event that governs key diapause traits, including ovarian developmental arrest and lipid accumulation. Conventionally, it is believed that the effects of JH are conveyed through the receptor Methoprene-tolerant (Met) and its transcriptional factor Krüppel homolog 1 (Kr-h1). However, our study with the bean bug Riptortus pedestris reveals that JH independently regulates lipid accumulation, bypassing Met and Kr-h1 pathways. R. pedestris enters reproduction under long-day (LD) conditions, while diapause occurs under short-day (SD) conditions. Treatment of SD females with the JH mimic methoprene stimulated reproductive activities, enhancing ovary development and reducing lipid accumulation. In contrast, silencing genes essential for JH biosynthesis in LD females led to pronounced diapause characteristics, including ovarian developmental arrest and substantial lipid accumulation. Interestingly, disruptions in the JH action genes, either Met or Kr-h1, solely affected ovary development, leaving lipid accumulation unchanged, indicating an independent pathway for regulating JH in lipid accumulation. This was further confirmed by RNA interference experiments in SD females, where knockdown of Met or Kr-h1 did not alter the effects of methoprene on lipid reduction. Collectively, these results suggest that JH controls ovary development through the established Met-Kr-h1 pathway, while it modulates lipid accumulation through an alternative, yet to be identified noncanonical pathway during reproductive diapause in R. pedestris.

A quest for the potato of the future: Characterization of wild tuber-bearing Solanum species for de novo domestication.

The potato (Solanum tuberosum) is a staple food worldwide, but modern potato cultivation relies heavily on the use of pesticides to control pests and diseases. However, many wild Solanum species are highly resistant to biotic and abiotic stresses relevant for potato production. Several of those species have been used in potato breeding to confer resistances which has only been moderately successful. Instead, we propose an alternative approach to utilize the potential of wild Solanum germplasm. Recently, de novo domestication has been suggested to create more resilient crops: Instead of introducing resistance genes into existing crops, domestication traits could be introduced into resistant wild crop relatives to create new crops. Therefore, we selected ten promising species from the 107 known wild tuber-bearing Solanum species for their resistance to biotic and abiotic stresses based on existing scientific literature for experimental characterization looking at tuberization under short and long-day conditions, tuber glycoalkaloid content, starch digestibility and performance in tissue culture. Based on this, the highly pest and disease resistant S. bulbocastanaum was chosen. Our results showed that it produced relatively large tubers, also under long-day conditions and performed exceptionally well in tissue culture.

Genome-wide characterization of PEBP genes in Mung bean (Vigna radiata L.) with functional analysis of VrFT1 in relation to photoperiod

Mung bean (Vigna radiata L.), a widely cultivated legume, belongs to the Fabaceae family’s Papilionoideae subfamily. Although Phosphatidylethanolamine-binding protein (PEBP) genes have been identified in several plant species, their presence and function in mung bean remain largely unexplored. In this study, we identified seven VrPEBP genes from mung bean and classified them into four clades: FT, MFT, TFL and FT-like. Cis-regulatory element analysis revealed that VrPEBP genes may play a role in light, hormone, and stress responses. Quantitative real-time PCR (qRT-PCR) analysis indicated that VrPEBPs were constitutively expressed in various tissues. However, tissue-specific expression patterns were observed among VrPEBP genes. Under short-day (SD) conditions, VrFT1 and VrMFT1 exhibited significantly higher expression levels than under long-day (LD) conditions at 8 and 4 h, respectively. Conversely, VrTFL2 and VrTFL3 showed significantly higher expression levels under LD conditions compared to SD conditions at 8 and 12 h, respectively. The varied expression patterns of these genes under different photoperiod suggest their potential involvement in the photoperiodic regulation of flowering in mung bean. Additionally, phenotypic analysis of transgenic Arabidopsis plants overexpressing VrFT1 revealed higher expression levels under SD conditions and predicted its role in promoting flowering. These results provide valuable insights into the evolution and function of PEBP genes in mung bean and lay the foundation for further research on their regulatory mechanisms and potential applications in mung bean improvement.

Rice ONAC005-OsMADS50-OsMADS56 interaction downregulates OsLFL1 in promoting long-day-dependent flowering

The transition from the vegetative to reproductive stage (flowering) is a critical stage in the life cycle of plants. Transition to flowering is controlled by a complex photoperiod-dependent network. Here, we report the functional analysis of NAC transcription factor ONAC005 as a positive regulator of flowering in rice. An onac005-1 T-DNA insertion mutant showed late flowering only under long-day (LD) conditions, indicating that ONAC005 is an LD-dependent flowering activator. Expression analysis of flowering time genes revealed that ONAC005 negatively regulates expression of OsLFL1, which is a LD-specific repressor of flowering in rice. Consequently, ONAC005 up-regulates expression of downstream genes Ehd1, Hd3a, and RFT1 under LD conditions. ONAC005 physically interacts with previously reported upstream regulators of OsLFL1, OsMADS50 and OsMADS56. Binding assays showed that ONAC005 binds to the promoter regions of OsLFL1. We further found that the ONAC005-OsMADS50-OsMADS56 complex weakly repressed OsLFL1 at the early vegetative stage and then gradually repressed it at the transcriptional level as the plant developed. Taken together, our results suggest that ONAC005 specifically affects flowering under LD-dependent conditions by interacting with an antagonistic protein complex.

Developing a pipeline for identification, characterization and molecular editing of cis-regulatory elements: a case study in potato

AbstractCrop breeding requires a balance of tradeoffs among key agronomic traits caused by gene pleiotropy. The molecular manipulation of genes can effectively improve target traits, but this may not reduce gene pleiotropy, potentially leading to undesirable traits or even lethal conditions. However, molecular editing of cis-regulatory elements (CREs) of target genes may facilitate the dissection of gene pleiotropy to fine-tune gene expression. In this study, we developed a pipeline, in potato, which employs open chromatin to predict candidate CREs, along with both transient and genetic assays to validate the function of CREs and CRISPR/Cas9 to edit candidate CREs. We used StCDF1 as an example, a key gene for potato tuberization and identified a 288 bp-core promoter region, which showed photoperiodic inducibility. A homozygous CRISPR/Cas9-editing line was established, with two deletions in the core promoter, which displayed a reduced expression level, resulting in late tuberization under both long-day and short-day conditions. This pipeline provides an alternative pathway to improve a specific trait with limited downside on other phenotypes.

Influence of Acute Inflammation on the Expression of Clock Genes in the Ovine Pars Tuberalis Under Different Photoperiodic Conditions.

The pars tuberalis (PT) plays an important role in the photoperiodic regulation of the secretory activity of the pituitary gland. Additionally, PT secretory activity may be influenced by the animal's immune status. The melatonin signal processing in PT cells occurs through the presence of melatonin receptors and the expression of molecular clock genes. This study aimed to define the effects of acute inflammation induced by intravenous administration of lipopolysaccharide (LPS) on the expression of clock genes in the PT of ewes under different photoperiodic conditions. Two analogous experiments were conducted in different photoperiods: short-day and long-day. Both experiments included 24 sheep divided into two groups: day (n = 12) and night (n = 12), further subdivided into a control group (n = 6) and a group treated with LPS (n = 6) at a dose of 400 ng/kg. Under short-day conditions, the expression of clock circadian regulator, basic helix-loop-helix ARNT like 1, cryptochrome circadian regulator (CRY) 1, 2, and casein kinase 1 epsilon genes was lower during inflammation. LPS injection increased expression of the period circadian regulator 1 gene during the night. Under long-day conditions, CRY1 mRNA level was lower during the night, while diurnal CRY2 mRNA expression was decreased after LPS injection. Our results showed that inflammation disturbed the expression of molecular clock genes in the PT; however, this influence was partly dependent on photoperiod conditions.

Post-Flowering Photoperiod Sensitivity of Soybean in Pod-Setting Responses.

The development of soybean (Glycine max) is regulated by the photoperiod, with genes related to photoperiod sensitivity primarily focused on the flowering time. However, their roles in post-flowering reproductive development and the mechanisms by which the photoperiod affects them are not yet determined. In this study, we found that pod formation is sensitive to the photoperiod. Long-day conditions tended to extend the time from flowering to pod formation, and the first wave of flowers tended to fall off. Additionally, the photoperiod affected the pistil morphology; under short-day conditions, the stigma had a curved hook-like structure that facilitated better interaction with the filaments when pollen was released, ultimately influencing the timing of pod formation. Photoperiod-insensitive mutants, lacking E1 family and Evening Complex (EC) genes, showed no difference in the pod formation time under long-day or short-day conditions. Hormone content analysis and transcriptome data analysis indicated that various hormones, reactive oxygen species (ROS) burst pathway signals, and the application of sucrose solution in vitro might influence floral organ abscission.

Both the Positioned Supplemental or Night-Interruptional Blue Light and the Age of Leaves (or Tissues) Are Important for Flowering and Vegetative Growth in Chrysanthemum.

In this study, the effects of supplemental or night interruptional blue light (S-BL or NI-BL) positioning on morphological growth, photoperiodic flowering, and expression of floral genes in Chrysanthemum morifolium were investigated. Blue light-emitting diodes (LEDs) at an intensity of 30 μmol·m-2·s-1 photosynthetic photon flux density (PPFD) were used for 4 h either (1) to supplement the white LEDs at the end of the 10 h short-day (SD10 + S-BL4) and 13 h long-day conditions (LD13 + S-BL4), or (2) to provide night interruption in the SD10 (SD10 + NI-BL4) and LD13 (LD13 + NI-BL4). The S-BL4 or NI-BL4 was positioned to illuminate either the shoot tip, the youngest leaf (vigorously growing the third leaf from the shoot tip), or the old leaf (the third leaf from the stem base). In the text, they will be denoted as follows: SD10 + S-BL4-S, -Y, or -O; SD10 + NI-BL4-S, -Y, or -O; LD13 + S-BL4-S, -Y, or -O; LD13 + NI-BL4-S, -Y, or -O. Normally, the LD13 conditions enhanced more vegetative growth than the SD10 periods. The growth of leaves, stems, and branches strongly responded to the S-BL4 or NI-BL4 when it was targeted onto the shoot tip, followed by the youngest leaf. The SD10 + S-BL4 or +NI-BL4 on the old leaf obviously suppressed plant extension growth, resulting in the smallest plant height. Under LD13 conditions, the flowering-related traits were significantly affected when the S-BL4 or NI-BL4 was shed onto the youngest leaf. However, these differences do not exist in the SD10 environments. At the harvest stage, other than the non-flowered LD13 treatment, the LD13 + S-BL4 irradiating the youngest leaf induced the most flowers, followed by the shoot tip and old leaf. Moreover, LD13 + NI-BL4 resulted in the latest flowering, especially when applied to the shoot tip and old leaf. However, the SD10 + S-BL4 or + NI-BL4 irradiated the shoot tip, youngest leaf, or old leaf all significantly earlier and increased flowering compared to the SD10 treatment. Overall: (1) Generally, vegetative growth was more sensitive to photoperiod rather than lighting position, while, during the same photoperiod, the promotion of growth was stronger when the light position of S-BL4 or NI-BL4 was applied to the shoot tip or the youngest leaf. (2) The photoperiodic flowering of these short-day plants (SDPs) comprehensively responded to the photoperiod combined with blue light positioning. Peculiarly, when they were exposed to the LD13 flowering-inhibited environments, the S-BL4 or NI-BL4 shed onto the leaves, especially the youngest leaves, significantly affecting flowering.

Metabolomic and transcriptomic basis of photoperiodic response regulation in broomcorn millet (Panicum miliaceum L.)

To elucidate the mechanisms underlying photoperiodic responses, we investigated the genomic and metabolomic responses of two broomcorn millet (Panicum miliaceum L.) genotypes. For this purpose, light-insensitive (D32) and light-sensitive (M51) genotypes were exposed to a 16 h photoperiod (long-day (LD) conditions) and an 8 h photoperiod (short-day (SD) conditions), and various transcriptomic and metabolomic changes were investigated. A total of 1664, 2564, 13,017, and 15548 DEGs were identified in the SD-D, LD-D, LD-M, and SD-M groups, respectively. Furthermore, 112 common DEGs were identified as well. Interestingly, most DEGs in the different groups were associated with photosynthesis and phenylpropanoid and carotenoid biosynthesis. In addition, 822 metabolites were identified under different treatments. The main metabolites, including L-malic and fumaric acids, were identified in the negative mode, whereas brucine and loperamide were identified in the positive mode. KEGG analysis revealed that the metabolites in the different groups were enriched in the same metabolic pathway of the TCA cycle. Furthermore, in negative mode, the metabolites of M51 were mainly D-glucose, whereas those of D32 were mainly L-malic and fumaric acids. One photoperiod candidate gene (C2845_PM11G01290), annotated as ATP6B, significantly increased the levels of L-malic and fumaric acids. In conclusion, our study provides a theoretical basis for understanding the molecular mechanisms of photoperiodic response regulation and can be used as a reference for marker development and resource identification in Panicum miliaceum L..

Integrated GWAS, linkage, and transcriptome analysis to identify genetic loci and candidate genes for photoperiod sensitivity in maize.

Maize photosensitivity and the control of flowering not only are important for reproduction, but also play pivotal roles in the processes of domestication and environmental adaptation, especially involving the utilization strategy of tropical maize in high-latitude regions. In this study, we used a linkage mapping population and an inbred association panel with the photoperiod sensitivity index (PSI) phenotyped under different environments and performed transcriptome analysis of T32 and QR273 between long-day and short-day conditions. The results showed that PSIs of days to tasseling (DTT), days to pollen shedding (DTP), and days to silking (DTS) indicated efficacious interactions with photoperiod sensitivity for maize latitude adaptation. A total of 48 quantitative trait loci (QTLs) and 252 quantitative trait nucleotides (QTNs) were detected using the linkage population and the inbred association panel. Thirteen candidate genes were identified by combining the genome-wide association study (GWAS) approach, linkage analysis, and transcriptome analysis, wherein five critical candidate genes, MYB163, bif1, burp8, CADR3, and Zm00001d050238, were significantly associated with photoperiod sensitivity. These results would provide much more abundant theoretical proofs to reveal the genetic basis of photoperiod sensitivity, which would be helpful to understand the genetic changes during domestication and improvement and contribute to reducing the barriers to use of tropical germplasm.