Short-day Conditions Research Articles

CRF12 specifically regulates the flowering time of Arabidopsis thaliana under non-inductive conditions.

The flowering time of Arabidopsis thaliana, a model plant, is significantly accelerated when exposed to long-day (LD) conditions, as it is a typical LD plant. Consequently, the investigation of the flowering regulatory network in A. thaliana under LD conditions has garnered considerable attention in the study of flowering signals, resulting in a significant breakthrough. While many LD plants, including A. thaliana, exhibit delayed flowering under non-inductive short-day (SD) conditions, they are still capable of flowering. Nevertheless, research on the regulation of flowering induction in LD plants under non-inductive SD conditions has been limited. This study demonstrated the involvement of CYTOKININ RESPONSE FACTORS 12 (CRF12) in the regulation of flowering in A. thaliana under non-inductive conditions. Analysis of the expression patterns revealed that the activation of CRF12 expression and protein stability occurred exclusively in non-inductive environments. Molecular and genetic analyses revealed that under a non-inductive photoperiod of 12 h of light and 12 h of darkness, CRF12, CONSTANS (CO), and TARGET OF EAT 1/2 (TOE1/2) engage in competitive interactions to regulate flowering time, while in a SD photoperiod of 8 h of light and 16 h of darkness, CRF12 modulates flowering time by inhibiting the activity of TOE1/2.

OsbZIP23 delays flowering by repressing OsMADS14 expression in rice

Flowering time is a fundamental factor determining the global distribution and final yield of rice (Oryza sativa L.). The initiation of the floral transition process signifies the beginning of the reproductive phase. The florigens Heading Date 3a (Hd3a) and Rice Flowering Locus T 1 (RFT1) combine with GF14 proteins and OsFD-like basic leucine zipper (bZIP) transcription factors to form florigen activation/repressor complexes (FACs/FRCs) that regulate the transition to flowering. We herein report that a bZIP transcription factor (OsbZIP23) functions as a flowering repressor. Transgenic plants overexpressing OsbZIP23 exhibited delayed flowering, which was in contrast to the slightly early flowering of the osbzip23 mutants, under natural short-day and long-day conditions. Molecular and biochemical analyses indicated that OsbZIP23 can bind to the 5′ untranslated region of OsMADS14 and suppress expression. Moreover, it delays the floral transition probably by interacting with OsFTL1/Hd3a/RFT1 and 14-3-3 proteins to form FRCs. Our findings have further elucidated the molecular mechanisms regulating the flowering time in rice.

Chinese cabbage orphan gene BR3 confers bolting resistance to Arabidopsis through the gibberellin pathway.

Premature bolting reduces the yield and quality of Chinese cabbage, making bolting resistance gene identification crucial for breeding superior and stable varieties. In this study, we identified an orphan gene BOLTING RESISTANCE 3 (BR3) that positively regulates bolting resistance in Arabidopsis thaliana. The expression of BR3 was developmentally regulated and occurred during the seedling and flowering stages. The BR3 protein was localized to both the plasma membrane and nucleus. Arabidopsis BR3 overexpressing (BR3OE) plants exhibited delayed bolting and flowering times, an increased number of rosette leaves, reduced plant height, and fewer siliques under long-day (LD) conditions. Key flowering genes were significantly downregulated in BR3OE plants. BR3OE plants similarly exhibited delayed bolting and flowering times, and an increased number of rosette leaves under short-day (SD) conditions. BR3OE plants showed no significant phenotypic differences after vernalization treatment. BR3OE and WT plants exhibited early flowering after GA3 treatment, and bolting and flowering time remained delayed in BR3OE plants compared with WT plants. Key DELLA genes BrRGA1 and BrRGL3 exhibited a co-expression pattern consistent with BR3 gene in Chinese cabbage, which suggested that BrRGA1 and BrRGL3 genes may directly or indirectly regulated by BR3 gene. BR3 gene increased bolting resistance perhaps by upregulating the expression of DELLA genes in the GA pathway. This study provides new theoretical insights for addressing premature bolting in Chinese cabbage and offers novel approaches for breeding bolting-resistant varieties.

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.

Night-break treatment with blue and green lights regulates erect thallus formation in the brown alga Petalonia fascia (KU-1293).

In this study, we investigated the photoperiodic responses regulating erect thallus formation in Petalonia fascia (KU-1293). We found that, through critical day length analysis and night break treatment culture experiments, P. fascia formed erect thalli under short-day conditions, indicating a genuine photoperiodic response. The critical day length for this morphological change was 10-11 h. Notably, night-break treatment with blue light (BL) and green light (GL) inhibited, whereas that with red light (RL) enhanced erect thallus formation. P. fascia was more sensitive to BL than to GL, requiring approximately 100-times less light to exhibit similar effects. Furthermore, promotion of erect thallus formation by RL was not negated by far-red light, suggesting the presence of a novel RL receptor distinct from the classical phytochrome system in terrestrial plants. These findings highlight the complexity of light wavelength interactions in regulating photoperiodic responses and suggest the presence of unique photoreceptors for day-length perception and erect thallus formation in P. fascia.

Endogenous H2S promotes Arabidopsis flowering through the regulation of GA20ox4 in the gibberellin pathway.

Flowering time is a critical determinant of plant reproductive success and agricultural yield. Hydrogen sulfide (H₂S), as a signaling molecule, regulates various aspects of plant growth and development. In this study, we examined the role of endogenous H₂S in regulating flowering time in Arabidopsis. The O-acetylserine thiol lyase a1 (oasa1) mutant, which has elevated H₂S levels due to impaired OASA1 activity that catalyzes the synthesis of Cys from H2S, flowers earlier than wild type (WT). The OASA1 overexpression lines (OE-OASA1-#33/#142), characterized by reduced H₂S levels, show delayed flowering, accompanied by decreased expression of key flowering regulators, FLOWERING LOCUS T (FT), SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), and AGAMOUS-LIKE24 (AGL24). Notably, vernalization and short-day (SD) conditions did not affect their flowering patterns. Exogenous H₂S and GA₃ treatment rescued the delayed flowering phenotype of OE-OASA1-#33/#142. In oasa1, levels of GA intermediates (GA15 and GA53) were elevated, while their levels were reduced in OE-OASA1-#33/#142. RT-qPCR analysis showed a significant reduction in the expression of GIBBERELLIN 20-OXIDASE 4 (GA20ox4) in OE-OASA1-#33/#142 compared to WT. Overexpression of GA20ox4 (OE-GA20ox4-#20/#30) resulted in earlier flowering and partially rescued the delayed flowering phenotype of OE-OASA1-#33/#142. Additionally, the expression of age pathway-related genes, including miRNA172b and SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 3/4/5/9/15 (SPL3/4/5/9/15), was significantly reduced in OE-OASA1-#33/#142 seedlings. These findings suggest that endogenous H₂S positively regulates GA20ox4 expression, thereby promoting gibberellin synthesis and advancing flowering in Arabidopsis through the GA pathway. Furthermore, the promotion of flowering by H₂S appears to be linked to the age pathway.

Molecular characterization of a novel photoperiod-insensitive allele Ppd-B1a.3 and its effect on heading date in Chinese wheat (Triticum aestivum) cultivar Qingchun 37.

Breeders adjust wheat heading dates to improve regional adaptability and reduce or mitigate yield losses caused by meteorological disasters, pests and diseases. The Ppd-1 genes play a crucial role in determining wheat sensitivity to changes in day-length and serve as key regulators of heading dates once the vernalization requirement is satisfied. In this study, we identified a new allelic variant of the promoter region, Ppd-B1a.3, in the Chinese wheat cultivar Qingchun 37. Compared to the Ppd-B1b.1 (carried by Chihokukomugi), the main mutation sites in Ppd-B1a.3 include a substitution of C with G at the -505-bp, a T base insertion at the -625-bp, a mutation of TCG to GGT at the -632 to -634-bp, and a 163-bp insertion at the -691bp. Analysis of F2 populations indicated that Ppd-B1a.3 promotes heading and flowering (approximately 6days earlier in population 1 and 17days in population 2) under short-day conditions in a greenhouse. However, the evaluation of Ppd-B1a.3's effect under field conditions may be influenced by the copy number of the Ppd-B1 locus inherited from the other parent in the F2 populations. Ppd-B1a.3 disrupts circadian rhythm expression and exhibits a stronger effect on heading and flowering than the three-copy Ppd-B1 allele carried by Jing 411. Origin analysis suggests that Ppd-B1a.3 may have derived from non-native germplasm. These results deepen our understanding of wheat photoperiod genes and provide useful genetic resources for fine-tuning wheat heading dates during breeding.

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.

Overwintering at multiple life stages in Schizotetranychus shii (Acari: Tetranychidae), a specialist of evergreen chinquapin.

Spider mites (Acari: Tetranychidae) overwinter as eggs or adult females, but some do so as multiple life stages on evergreen hosts. However, proximate factors influencing such overwintering stages remain poorly understood. This study investigated photoperiodic responses and life-stage compositions during winter in a population of Schizotetranychus shii, a specialist of Japanese chinquapin (Fagaceae). The proportion of non-ovipositing females at 20°C followed a sigmoid curve with increasing photoperiod. The critical day length was estimated as a photoperiod of 11.8h light and 12.2h dark (11.8L), which was similar to the natural photoperiod from late September to early October. Although females grown under 10L and 11L conditions never oviposited within 7days, 90-96% of them started oviposition within 30days without chilling, indicating shallow reproductive diapause. In the field, all life stages occurred throughout winter, but their proportions varied considerably. The proportion of eggs declined from early October (62%) to early December (12%), as predicted by the critical day length, but steeply increased toward late February (96%), in which only adult females and eggs remained. These findings suggest that short-day conditions in the field do not maintain adult diapause as predicted by the above experiment. In summary, a short photoperiod in October or November arrests oviposition in emerging females, but they commence oviposition during the short-day season when immature stages are still growing. As a result, individuals at all life stages coexist until all immature stages mature in February.

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.

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.

Integrated eQTL mapping approach reveals genomic regions regulating candidate genes of the E8-r3 locus in soybean.

Deciphering the gene regulatory networks of critical quantitative trait loci associated with early maturity provides information for breeders to unlock soybean's (Glycine max (L.) Merr.) northern potential and expand its cultivation range. The E8-r3 locus is a genomic region regulating the number of days to maturity under constant short-day photoperiodic conditions in two early-maturing soybean populations (QS15524F2:F3 and QS15544RIL) belonging to maturity groups MG00 and MG000. In this study, we developed a combinatorial expression quantitative trait loci mapping approach using three algorithms (ICIM, IM, and GCIM) to identify the regions that regulate three candidate genes of the E8-r3 locus (Glyma.04G167900/GmLHCA4a, Glyma.04G166300/GmPRR1a, and Glyma.04G159300/GmMDE04). Using this approach, a total of 2,218 trans (2,061 genes)/7 cis (7 genes) and 4,073 trans (2,842 genes)/3,083 cis (2,418 genes) interactions were mapped in the QS15524F2:F3 and QS15544RIL populations, respectively. From these interactions, we successfully identified two hotspots (F2_GM15:49,385,092-49,442,237 and F2_GM18:1,434,182-1,935,386) and three minor regions (RIL_GM04:17,227,512-20,251,662, RIL_GM04:31,408,946-31,525,671 and RIL_GM13:37,289,785-38,620,690) regulating the candidate genes of E8-r3 and several of their homologs. Based on co-expression network and single nucleotide variant analyses, we identified ALTERED PHLOEM DEVELOPMENT (Glyma.15G263700) and DOMAIN-CONTAINING PROTEIN 21 (Glyma.18G025600) as the best candidates for the F2_GM15:49,385,092-49,442,237 and F2_GM18:1,434,182-1,935,386 hotspots. These findings demonstrate that a few key regions are involved in the regulation of the E8-r3 candidates GmLHCA4a, GmPRR1a, and GmMDE04.

Carbon and nitrogen signaling regulate FLOWERING LOCUS C and impact flowering time in Arabidopsis.

The timing of flowering in plants is modulated by both carbon (C) and nitrogen (N) signaling pathways. In a previous study, we established a pivotal role of the sucrose-signaling trehalose 6-phosphate pathway in regulating flowering under N-limited short-day conditions. In this work, we show that both wild-type Arabidopsis (Arabidopsis thaliana) plants grown under N-limited conditions and knock-down plants of TREHALOSE PHOSPHATE SYNTHASE 1 induce FLOWERING LOCUS C (FLC) expression, a well-known floral repressor associated with vernalization. When exposed to an extended period of cold, a flc mutant fails to respond to N availability and flowers at the same time under N-limited and full-nutrition conditions. Our data suggest that SUCROSE NON-FERMENTING 1 RELATED KINASE 1-dependent trehalose 6-phosphate-mediated C signaling and a mechanism downstream of N signaling (likely involving NIN-LIKE PROTEIN 7) impact the expression of FLC. Collectively, our data underscore the existence of a multi-factor regulatory system in which the C and N signaling pathways jointly govern the regulation of flowering in plants.

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.

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.

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.

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.

Modulation of the Arabidopsis Starch Metabolic Network by the Cytosolic Acetyl-CoA Pathway in the Context of the Diurnal Illumination Cycle

The starch metabolic network was investigated in relation to other metabolic processes by examining a mutant with altered single-gene expression of ATP citrate lyase (ACL), an enzyme responsible for generating cytosolic acetyl-CoA pool from citrate. Previous research has shown that transgenic antisense plants with reduced ACL activity accumulate abnormally enlarged starch granules. In this study, we explored the underlying molecular mechanisms linking cytosolic acetyl-CoA generation and starch metabolism under short-day photoperiods. We performed transcriptome and quantification of starch accumulation in the leaves of wild-type and antisense seedlings with reduced ACL activity. The antisense-ACLA mutant accumulated more starch than the wild type under short-day conditions. Zymogram analyses were conducted to compare the activities of starch-metabolizing enzymes with transcriptomic changes in the seedling. Differential expression between wild-type and antisense-ACLA plants was detected in genes implicated in starch and acetyl-CoA metabolism, and cell wall metabolism. These analyses revealed a strong correlation between the transcript levels of genes responsible for starch synthesis and degradation, reflecting coordinated regulation at the transcriptomic level. Furthermore, our data provide novel insights into the regulatory links between cytosolic acetyl-CoA metabolism and starch metabolic pathways.

Heading Date 3a Stimulates Tiller Bud Outgrowth in Oryza sativa L. through Strigolactone Signaling Pathway.

Heading date 3a (Hd3a, a FLOWERING LOCUS T (FT) ortholog from rice) is well known for its important role in rice (Oryza sativa L.), controlling floral transition under short-day (SD) conditions. Although the effect of Hd3a on promoting branching has been found, the underlying mechanism remains largely unknown. In this report, we overexpressed an Hd3a and BirAG (encoding a biotin ligase) fusion gene in rice, and found that early flowering and tiller bud outgrowth was promoted in BHd3aOE transgenic plants. On the contrary, knockout of Hd3a delayed flowering and tiller bud outgrowth. By using the BioID method, we identified multiple Hd3a proximal proteins. Among them, D14, D53, TPR1, TPR2, and TPRs are central components of the strigolactone signaling pathway, which has an inhibitory effect on rice tillering. The interaction between Hd3a, on the one hand, and D14 and D53 was further confirmed by the bimolecular fluorescence complementation (BiFC), yeast two-hybrid (Y2H), and co-immunoprecipitation (Co-IP) methods. We also found that Hd3a prevented the degradation of D53 induced by rac-GR24 (a strigolactone analog) in rice protoplasts. RT-qPCR assay showed that the expression levels of genes involved in strigolactone biosynthesis and signal transduction were altered significantly between WT and Hd3a overexpression (Hd3aOE) or mutant (hd3a) plants. OsFC1, a downstream target of the strigolactone signaling transduction pathway in controlling rice tillering, was downregulated significantly in Hd3aOE plants, whereas it was upregulated in hd3a lines. Collectively, these results indicate that Hd3a promotes tiller bud outgrowth in rice by attenuating the negative effect of strigolactone signaling on tillering and highlight a novel molecular network regulating rice tiller outgrowth by Hd3a.

Metabolomics, phytohormone and transcriptomics strategies to reveal the mechanism of barley heading date regulation to responds different photoperiod

BackgroundThe correlation between heading date and flowering time significantly regulates grain filling and seed formation in barley and other crops, ultimately determining crop productivity. In this study, the transcriptome, hormone content detection, and metabolome analysis were performed systematically to analyze the regulatory mechanism of heading time in highland barley under different light conditions. The heading date of D18 (winter highland barley variety, Dongqing18) was later than that of K13 (vernal highland barley variety) under normal growth conditions or long-day (LD) treatment, while this situation will reverse with short-day (SD) treatment.ResultsThe circadian rhythm plant, plant hormone signaling transduction, starch and sucrose metabolism, and photosynthesis-related pathways are significantly enriched in barley under SD and LD to influence heading time. In the plant circadian rhythm pathway, the key genes GI (Gigantea), PRR (Pesudoresponseregulator), FKF1 (Flavin-binding kelch pepeat F-Box 1), and FT (Flowering locus T) are identified as highly expressed in D18SD3 and K13SD2, while they are significantly down-regulated in K13SD3. These genes play an important role in regulating the heading date of D18 earlier than that of K13 under SD conditions. In photosynthesis-related pathways, a-b binding protein and RBS were highly expressed in K13LD3, while NADP-dependent malic enzyme, phosphoenolpyruvate carboxylase, fructose-bisphosphate aldolase, and triosephosphate isomerase were significantly expressed in D18SD3. In the starch and sucrose metabolism pathway, 41 DEGs (differentially expressed genes) and related metabolites were identified as highly expressed and accumulated in D18SD3. The DEGs SAUR (Small auxin-up RNA), ARF (Auxin response factor), TIR1 (Transport inhibitor response 1), EIN3 (Ethylene-insensitive 3), ERS1 (Ethylene receptor gene), and JAZ1 (Jasmonate ZIM-domain) in the plant hormone pathway were significantly up-regulated in D18SD3. Compared with D18LD3, the content of N6-isopentenyladenine, indole-3-carboxylic acid, 1-aminocyclopropanecarboxylic acid, trans-zeatin, indole-3-carboxaldehyde, 1-O-indol-3-ylacetylglucose, and salicylic acid in D18SD3 also increased. The expression levels of vernalization genes (HvVRN1, HvVRN2, and HvVRN3), photoperiod genes (PPD), and PPDK (Pyruvate phosphate dikinase) that affect photosynthetic efficiency in barley are also analyzed, which play important regulatory roles in barley heading date. The WGCNA analysis of the metabolome data and circadian regulatory genes identified the key metabolites and candidate genes to regulate the heading time of barley in response to the photoperiod.ConclusionThese studies will provide a reference for the regulation mechanism of flowering and the heading date of highland barley.