Regulation Of Flowering Time Research Articles

Genome-wide characterization of PEBP family genes in nine Rosaceae tree species and their expression analysis in P. mume

BackgroundPhosphatidylethanolamine-binding proteins (PEBPs) constitute a common gene family found among animals, plants and microbes. Plant PEBP proteins play an important role in regulating flowering time, plant architecture as well as seed dormancy. Though PEBP family genes have been well studied in Arabidopsis and other model species, less is known about these genes in perennial trees.ResultsTo understand the evolution of PEBP genes and their functional roles in flowering control, we identified 56 PEBP members belonging to three gene clades (MFT-like, FT-like, and TFL1-like) and five lineages (FT, BFT, CEN, TFL1, and MFT) across nine Rosaceae perennial species. Structural analysis revealed highly conserved gene structure and protein motifs among Rosaceae PEBP proteins. Codon usage analysis showed slightly biased codon usage across five gene lineages. With selection pressure analysis, we detected strong purifying selection constraining divergence within most lineages, while positive selection driving the divergence of FT-like and TFL1-like genes from the MFT-like gene clade. Spatial and temporal expression analyses revealed the essential role of FT in regulating floral bud breaking and blooming in P. mume. By employing a weighted gene co-expression network approach, we inferred a putative FT regulatory module required for dormancy release and blooming in P. mume.ConclusionsWe have characterized the PEBP family genes in nine Rosaceae species and examined their phylogeny, genomic syntenic relationship, duplication pattern, and expression profiles during flowering process. These results revealed the evolutionary history of PEBP genes and their functions in regulating floral bud development and blooming among Rosaceae tree species.

Two B-box domain proteins, BBX28 and BBX29, regulate flowering time at low ambient temperature in Arabidopsis

This paper demonstrates that BBX28 and BBX29 proteins in Arabidopsis promote flowering in association with the CO-FT regulatory module at low ambient temperature under LD conditions. Flowering plants integrate internal developmental signals with external environmental stimuli for precise flowering time control. The expression of BBX29 is up-regulated by low temperature treatment, but the biological function of BBX29 in low temperature response is unknown. In the current study, we examined the biological role of BBX29 and its close-related protein BBX28 in flowering time control under long-day conditions. Although neither BBX28 single mutant nor BBX29 single mutant has a flowering-associated phenotype, the bbx28 bbx29 double mutant plants have an obvious delayed flowering phenotype grown at low ambient temperature (16°C) compared to the wild-type (WT) plants. The expression of FT and TSF was lower in bbx28 bbx29 double mutant plants than in wild-type plants at 16°C. Both BBX28 and BBX29 interact with CONSTANS (CO), an important flowering integrator that directly binds to the FLOWERING LOCUS T (FT) promoter. In the effector-reporter assays, transcriptional activation activity of CO on the FT promoter was reduced in bbx28 bbx29 double mutant plants compared to that in WT plants. Taken together, our results reveal that BBX28 and BBX29 are promoters of flowering in Arabidopsis, especially at low ambient temperature.

Characterization of Mungbean CONSTANS-LIKE Genes and Functional Analysis of CONSTANS-LIKE 2 in the Regulation of Flowering Time in Arabidopsis.

CONSTANS-LIKE (COL) genes play important roles in the regulation of plant growth and development, and they have been analyzed in many plant species. However, few studies have examined COL genes in mungbean (Vigna radiata). In this study, we identified and characterized 31 mungbean genes whose proteins contained B-Box domains. Fourteen were designated as VrCOL genes and were distributed on 7 of the 11 mungbean chromosomes. Based on their phylogenetic relationships, VrCOLs were clustered into three groups (I, II, and III), which contained 4, 6, and 4 members, respectively. The gene structures and conserved motifs of the VrCOL genes were analyzed, and two duplicated gene pairs, VrCOL1/VrCOL2 and VrCOL8/VrCOL9, were identified. A total of 82 cis-acting elements were found in the VrCOL promoter regions, and the numbers and types of cis-acting elements in each VrCOL promoter region differed. As a result, the expression patterns of VrCOLs varied in different tissues and throughout the day under long-day and short-day conditions. Among these VrCOL genes, VrCOL2 showed a close phylogenetic relationship with Arabidopsis thaliana CO and displayed daily oscillations in expression under short-day conditions but not long-day conditions. In addition, overexpression of VrCOL2 accelerated flowering in Arabidopsis under short-day conditions by affecting the expression of the flowering time genes AtFT and AtTSF. Our study lays the foundation for further investigation of VrCOL gene functions.

Quantitative Trait Locus Mapping and Identification of Candidate Genes Controlling Flowering Time in Brassica napus L.

Flowering time plays a vital role in determining the life-cycle period, yield, and seed quality of rapeseed (Brassica napus L.) in certain environments. Quantitative trait locus (QTL) mapping to identify the genetic architecture of genes controlling flowering time helps accelerate the early maturity breeding process. In this study, simple sequence repeats (SSR) and specific-locus amplified fragment sequencing (SLAF-seq) technologies were adopted to map the QTLs for flowering time in four environments. As a result, three target intervals, FTA09, FTA10, and FTC05 were identified. Among this, FTA09 was considered as a novel interval, FTA10 and FTC05 as stable regions. Based on the parental re-sequencing data, 7,022 single nucleotide polymorphisms (SNPs) and 2,195 insertion-deletions (InDels) between the two parents were identified in these three target regions. A total of 186 genes possessed genetic variations in these intervals, 14 of which were related to flowering time involved in photoperiod, circadian clock, vernalization, and gibberellin pathways. Six InDel markers linked to flowering time were developed in the three target intervals, indicating that the results were credible in this study. These results laid a good foundation for further genetic studies on flowering-time regulation in B. napus L.

Hydrogen sulfide promotes flowering in heading Chinese cabbage by S-sulfhydration of BraFLCs

Heading Chinese cabbage (Brassica rapa L. syn. B. campestris L. ssp. chinensis Makino var. pekinensis (Rupr.) J. Cao et Sh. Cao) is a cruciferous Brassica vegetable that has a triplicate genome, owing to an ancient genome duplication event. It is unclear whether the duplicated homologs have conserved or diversified functions. Hydrogen sulfide (H2S) is a plant gasotransmitter that plays important physiological roles in growth, development, and responses to environmental stresses. The modification of cysteines through S-sulfhydration is an important mechanism of H2S, which regulates protein functions. H2S promotes flowering in Arabidopsis and heading Chinese cabbage. Here we investigated the molecular mechanisms of H2S used to promote flowering in the latter. Four, five, and four BraFLC, BraSOC I, and BraFT homologs were identified in heading Chinese cabbage. Different BraFLC proteins were bound to different CArG boxes in the promoter regions of the BraSOC I and BraFT homologs, producing different binding patterns. Thus, there may be functionally diverse BraFLC homologs in heading Chinese cabbage. Exogenous H2S at 100 μmol L−1 significantly promoted flowering by compensating for insufficient vernalization. BraFLC 1 and BraFLC 3 underwent S-sulfhydration by H2S, after which their abilities to bind most BraSOC I or BraFT promoter probes weakened or even disappeared. These changes in binding ability were consistent with the expression pattern of the BraFT and BraSOC I homologs in seedlings treated with H2S. These results indicated that H2S signaling regulates flowering time. In summary, H2S signaling promoted plant flowering by weakening or eliminating the binding abilities of BraFLCs to downstream promoters through S-sulfhydration.

English

Chia (Salvia hispanica), originated in Mexico, has outstanding nutritional and health-promoting values, but it is the only ancient American Indian staple crop failed in introduction to the Old Continents. After the rediscovery and revival of chia as a new crop in recent years, the short-day (SD) habit is a crucial limitation for its worldwide cultivation. The circadian oscillator GIGNATEA (GI) is an important transcription factor regulating flowering time through photoperiod-pathway. In this study, we cloned the full-length cDNAs of two GI genes from chia, and analyzed the molecular characteristics of the genes and the encoded proteins. Alternative transcription initiation sites, alternative poly A tailing sites, and 5’-UTR intron retention exist in some of their mRNAs. The origin of GI gene accompanied with the transition from aquatic to terrestrial habits during plant evolution. GI duplication events occurred at order, family and genus levels in angiosperms. ShGI-1 and ShGI-2 were similar to each other in organ specificity with peak expression in small buds. In mature leaf, ShGI-2 is dominant over ShGI-1 in terms of expression level with highest expression in the afternoon, but on the Autumnal Equinox day ShGI-1 is dominant over ShGI-2 with peaks at noon and in the evening. KT, BR, GA3 and IAA upregulated the expression of ShGI-1 and ShGI-2 in long-days (LDs) and inhibited their expression in SDs, with GA3 being the most effective phytohormone. Under most abiotic stresses, ShGI expression fluctuated and returned to near-basal levels. ShGI expression was upregulated by low temperature. SA sharply upregulated ShGI expression after 24 h of treatment. This is the first report of GI genes from the order Lamiales, which will promote the dissection of flowering mechanism of chia and other Lamiales plants, enrich the evolution and expression characteristics of plant GIs, and promote the study on interaction between photoperiod and hormone pathways in flowering time control. © 2021 Friends Science Publishers

Identification and characterization of regulatory pathways involved in early flowering in the new leaves of alfalfa (Medicago sativa L.) by transcriptome analysis

BackgroundAlfalfa (Medicago sativa L.) is a perennial legume extensively planted throughout the world as a high nutritive value livestock forage. Flowering time is an important agronomic trait that contributes to the production of alfalfa hay and seeds. However, the underlying molecular mechanisms of flowering time regulation in alfalfa are not well understood.ResultsIn this study, an early-flowering alfalfa genotype 80 and a late-flowering alfalfa genotype 195 were characterized for the flowering phenotype. Our analysis revealed that the lower jasmonate (JA) content in new leaves and the downregulation of JA biosynthetic genes (i.e. lipoxygenase, the 12-oxophytodienoate reductase-like protein, and salicylic acid carboxyl methyltransferase) may play essential roles in the early-flowering phenotype of genotype 80. Further research indicated that genes encode pathogenesis-related proteins [e.g. leucine rich repeat (LRR) family proteins, receptor-like proteins, and toll-interleukin-like receptor (TIR)-nucleotide-binding site (NBS)-LRR class proteins] and members of the signaling receptor kinase family [LRR proteins, kinases domain of unknown function 26 (DUF26) and wheat leucine-rich repeat receptor-like kinase10 (LRK10)-like kinases] are related to early flowering in alfalfa. Additionally, those involved in secondary metabolism (2-oxoglutarate/Fe (II)-dependent dioxygenases and UDP-glycosyltransferase) and the proteasome degradation pathway [really interesting new gene (RING)/U-box superfamily proteins and F-box family proteins] are also related to early flowering in alfalfa.ConclusionsIntegrated phenotypical, physiological, and transcriptomic analyses demonstrate that hormone biosynthesis and signaling pathways, pathogenesis-related genes, signaling receptor kinase family genes, secondary metabolism genes, and proteasome degradation pathway genes are responsible for the early flowering phenotype in alfalfa. This will provide new insights into future studies of flowering time in alfalfa and inform genetic improvement strategies for optimizing this important trait.

Overexpression of AGAMOUS-like gene PfAG5 promotes early flowering in Polypogon fugax.

Herbicides are the major tool for controlling large populations of yield depleting weeds. However, over-reliance on herbicides has resulted in weed adaptation and herbicide resistance. In recent years, early flowering weed species related to herbicide resistance is emerging, which may cause seed loss before crop harvest, creating a new problem for non-chemical weed management. In this study, a homologue gene of AGAMOUS sub-family (referred to as PfAG5) of the MADS-box family was cloned from plants of an early flowering Polypogon fugax Nees ex Steud. population resistant to the ACCase inhibitor herbicide (clodinafop-propargyl). The PfAG5 gene was functionally characterised in Arabidopsis thaliana L. Overexpression of the PfAG5 gene in Arabidopsis resulted in early flowering, abnormal flowers (e.g. small petals), short plants and reduced seed set, compared with the wild type. The expression of the PfAG5 gene was high in leaves and flowers, but low in pods in transgenic Arabidopsis. The PfAG5 gene was expressed earlier and higher in the resistant (R) than the susceptible (S) P. fugax plants. Furthermore, one protein (FRIGIDA-like) with relevance to flowering time regulation and interacts with PfAG5 in resistant (R) P. fugax was identified by the yeast two-hybrid and pull-down assays. These results suggest that the PfAG5 gene is involved in modulating early flowering in P. fugax.

The Role of FLOWERING LOCUS C Relatives in Cereals.

FLOWERING LOCUS C (FLC) is one of the best characterized genes in plant research and is integral to vernalization-dependent flowering time regulation. Yet, despite the abundance of information on this gene and its relatives in Arabidopsis thaliana, the role FLC genes play in other species, in particular cereal crops and temperate grasses, remains elusive. This has been due in part to the comparative reduced availability of bioinformatic and mutant resources in cereals but also on the dominant effect in cereals of the VERNALIZATION (VRN) genes on the developmental process most associated with FLC in Arabidopsis. The strong effect of the VRN genes has led researchers to believe that the entire process of vernalization must have evolved separately in Arabidopsis and cereals. Yet, since the confirmation of the existence of FLC-like genes in monocots, new light has been shed on the roles these genes play in both vernalization and other mechanisms to fine tune development in response to specific environmental conditions. Comparisons of FLC gene function and their genetic and epigenetic regulation can now be made between Arabidopsis and cereals and how they overlap and diversify is coming into focus. With the advancement of genome editing techniques, further study on these genes is becoming increasingly easier, enabling us to investigate just how essential FLC-like genes are to modulating flowering time behavior in cereals.

Distinct Preflowering Drought Tolerance Strategies of Sorghum bicolor Genotype RTx430 Revealed by Subcellular Protein Profiling.

Drought is the largest stress affecting agricultural crops, resulting in substantial reductions in yield. Plant adaptation to water stress is a complex trait involving changes in hormone signaling, physiology, and morphology. Sorghum (Sorghum bicolor (L.) Moench) is a C4 cereal grass; it is an agricultural staple, and it is particularly drought-tolerant. To better understand drought adaptation strategies, we compared the cytosolic- and organelle-enriched protein profiles of leaves from two Sorghum bicolor genotypes, RTx430 and BTx642, with differing preflowering drought tolerances after 8 weeks of growth under water limitation in the field. In agreement with previous findings, we observed significant drought-induced changes in the abundance of multiple heat shock proteins and dehydrins in both genotypes. Interestingly, our data suggest a larger genotype-specific drought response in protein profiles of organelles, while cytosolic responses are largely similar between genotypes. Organelle-enriched proteins whose abundance significantly changed exclusively in the preflowering drought-tolerant genotype RTx430 upon drought stress suggest multiple mechanisms of drought tolerance. These include an RTx430-specific change in proteins associated with ABA metabolism and signal transduction, Rubisco activation, reactive oxygen species scavenging, flowering time regulation, and epicuticular wax production. We discuss the current understanding of these processes in relation to drought tolerance and their potential implications.

Flowering time regulation model revisited by pooled sequencing of mass selection populations

Maize is one of the most broadly cultivated crops throughout the world, and flowering time is a major adaptive trait for its diffusion. The biggest challenge in understanding maize flowering genetic architecture is that the trait is confounded with population structure. To eliminate the effect, we revisited the flower time genetic network by using a tropical maize population Pop32, which was under mass selection for adaptation to early flowering time in China for six generations from tropical to temperate regions. The days to anthesis (DTA) of the initial (Pop32C0), intermedia (Pop32C3), and final population (Pop32C5) was 90.77, 84.63, and 79.72 days on average, respectively. To examine the genetic mechanism and identify the genetic loci underlying this rapid change in flowering time of Pop32, we bulked 30 individuals from C0, C3, and C5 to conduct the whole genome sequencing. And we finally identified 4,973,810 high-quality single nucleotide polymorphisms (SNPs) and 6,517 genes with allele frequency significantly changed during the artificial improvement process. We speculate that these genes might participate in the adaptive improvement process and control flowering time. To identify the candidate genes for flowering time from the gene set with allele frequency changed, we carried out weighted gene co-expression network analysis (WGCNA), and identified four co-expression modules that highly associated with the flowering time development, as well as constructed the co-expression network of key flowering time genes. Gene Ontology (GO) enrichment analysis revealed that the GO terms photosynthesis/light reaction, carbohydrate binding, auxin mediated signaling pathway, response to temperature stimulus that are closely connected with flowering time. Furthermore, targeted GWAS revealed the genes are significantly connected with the flowering time. qRT-PCR of four candidate genes GRMZM2G019879, GRMZM2G055905, GRMZM2G058158, and GRMZM2G171365 showed that their expression level is similar to the flowering time genes, which playing a key role in maize flowering time transition. This study revealed that the changes of flowering time in mass selection process may be strongly associated with the variations of allele frequency changes, and we identified some important candidate genes for flowering time, which will provide a new insight for the rapid improvement of maize important agronomic traits and promote the gene cloning of maize flowering time.

Overexpression of AtAHL20 causes delayed flowering in Arabidopsis via repression of FT expression

BackgroundThe 29-member Arabidopsis AHL gene family is classified into three main classes based on nucleotide and protein sequence evolutionary differences. These differences include the presence or absence of introns, type and/or number of conserved AT-hook and PPC domains. AHL gene family members are divided into two phylogenetic clades, Clade-A and Clade-B. A majority of the 29 members remain functionally uncharacterized. Furthermore, the biological significance of the DNA and peptide sequence diversity, observed in the conserved motifs and domains found in the different AHL types, is a subject area that remains largely unexplored.ResultsTransgenic plants overexpressing AtAHL20 flowered later than the wild type under both short and long days. Transcript accumulation analyses showed that 35S:AtAHL20 plants contained reduced FT, TSF, AGL8 and SPL3 mRNA levels. Similarly, overexpression of AtAHL20’s orthologue in Camelina sativa, Arabidopsis’ closely related Brassicaceae family member species, conferred a late-flowering phenotype via suppression of CsFT expression. However, overexpression of an aberrant AtAHL20 gene harboring a missense mutation in the AT-hook domain’s highly conserved R-G-R core motif abolished the late-flowering phenotype. Data from targeted yeast-two-hybrid assays showed that AtAHL20 interacted with itself and several other Clade-A Type-I AHLs which have been previously implicated in flowering-time regulation: AtAHL19, AtAHL22 and AtAHL29.ConclusionWe showed via gain-of-function analysis that AtAHL20 is a negative regulator of FT expression, as well as other downstream flowering time regulating genes. A similar outcome in Camelina sativa transgenic plants overexpressing CsAHL20 suggest that this is a conserved function. Our results demonstrate that AtAHL20 acts as a photoperiod-independent negative regulator of transition to flowering.

AGL19 directly interacts with floral signal integrator AGL24 in flowering time control of Brassica juncea

SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) and AGAMOUS-LIKE 24 (AGL24) are pivotal flowering signal integrators, which respectively, belong to TM3/SOC1 and STMADS11 clades of MIKC-type MADS-box family. AGAMOUS-LIKE 19 (AGL19), one member of TM3/SOC1 clade family, acts as an activator of flowering time. Previous studies have suggested that AGL19 together with AGL24 and SOC1 coordinately regulate flowering time. However, it remains unknown how AGL19 interacts with SOC1 and AGL24 in Brassica juncea. Here, an AGL19-like (BjuAGL19) was cloned from B. juncea, which was expressed in roots, stems, leaves, buds and flowers. Furthermore, both yeast one-hybrid and Dual-Glo Luciferase assays confirmed that BjuAGL19 protein could not target the promoters of BjuSOC1 and BjuAGL24. Interestingly, based on yeast two-hybrid and pull-down assays, BjuAGL19 protein directly interacted with BjuAGL24 protein, instead of BjuSOC1 protein. It is speculated that BjuAGL19 can bind to BjuAGL24 to form protein complex of BjuAGL19-BjuAGL24 and thus regulates flowering time in B. juncea. The results are very helpful for further elucidating the molecular mechanism of BjuAGL19 in flowering time control.

Molecular variation in a functionally divergent homolog of FCA regulates flowering time in Arabidopsis thaliana

The identification and functional characterization of natural variants in plants are essential for understanding phenotypic adaptation. Here we identify a molecular variation in At2g47310 that contributes to the natural variation in flowering time in Arabidopsis thaliana accessions. This gene, which we term SISTER of FCA (SSF), functions in an antagonistic manner to its close homolog FCA. Genome-wide association analysis screens two major haplotypes of SSF associated with the natural variation in FLC expression, and a single polymorphism, SSF-N414D, is identified as a main contributor. The SSF414N protein variant interacts more strongly with CUL1, a component of the E3 ubiquitination complex, than the SSF414D form, mediating differences in SSF protein degradation and FLC expression. FCA and SSF appear to have arisen through gene duplication after dicot-monocot divergence, with the SSF-N414D polymorphism emerging relatively recently within A. thaliana. This work provides a good example for deciphering the functional importance of natural polymorphisms in different organisms.

FLC and SVP Are Key Regulators of Flowering Time in the Biennial/Perennial Species Noccaea caerulescens.

The appropriate timing of flowering is crucial for plant reproductive success. Studies of the molecular mechanism of flower induction in the model plant Arabidopsis thaliana showed long days and vernalization as major environmental promotive factors. Noccaea caerulescens has an obligate vernalization requirement that has not been studied at the molecular genetics level. Here, we characterize the vernalization requirement and response of four geographically diverse biennial/perennial N. caerulescens accessions: Ganges (GA), Lellingen (LE), La Calamine (LC), and St. Felix de Pallières (SF). Differences in vernalization responsiveness among accessions suggest that natural variation for this trait exists within N. caerulescens. Mutants which fully abolish the vernalization requirement were identified and were shown to contain mutations in the FLOWERING LOCUS C (NcFLC) and SHORT VEGETATIVE PHASE (NcSVP) genes, two key floral repressors in this species. At high temperatures, the non-vernalization requiring flc-1 mutant reverts from flowering to vegetative growth, which is accompanied with a reduced expression of LFY and AP1. This suggested there is “crosstalk” between vernalization and ambient temperature, which might be a strategy to cope with fluctuations in temperature or adopt a more perennial flowering attitude and thus facilitate a flexible evolutionary response to the changing environment across the species range.

Expansion and expression diversity of FAR1/FRS-like genes provides insights into flowering time regulation in roses

Roses are important horticultural plants with enormous diversity in flowers and flowering behavior. However, molecular regulation of flowering time variation in roses remains poorly characterized. Here, we report an expansion of the FAR1/FRS-like genes that correlates well with the switch to prostrate-to-erect growth of shoots upon flowering in Rosa wichuraiana ‘Basye's Thornless' (BT). With the availability of the high-quality chromosome-level genome assembly for BT that we developed recently, we identified 91 RwFAR1/FRS-like genes, a significant expansion in contrast to 52 in Rosa chinensis ‘Old Blush’ (OB), a founder genotype in modern rose domestication. Rose FAR1/FRS-like proteins feature distinct variation in protein domain structures. The dispersed expansion of RwFAR1/FRS-like genes occurred specifically in clade I and II and is significantly associated with transposon insertion in BT. Most of the RwFAR1/FRS-like genes showed relatively higher expression level than their corresponding orthologs in OB. FAR1/FRS-like genes regulate light-signaling processes, shade avoidance, and flowering time in Arabidopsis thaliana. Therefore, the expansion and duplication of RwFAR1/FRS-like genes, followed by diversification in gene expression, might offer a novel leverage point for further understanding the molecular regulation of the variation in shoot-growth behavior and flowering time in roses.

BnSIP1-1 Involves in Light Response and Regulation of Endogenous Hormones and Flowering Time of Brassica Napus

BnSIP1-1 is a trihelix transcription factor family gene which functions in abiotic stress response and abscisic acid (ABA) signaling during seed germination and seedling growth of Brassica napus. In the present study, further sequence analysis and phenotype identification indicated that this gene had roles in light regulation and flowering of reproductive growth stage. Many phytohormones responsive cis-acting elements, including TC-rich repeats, GARE-motif, and TCA and TGA elements, were identified in the promoter sequence of BnSIP1-1. The expression of BnSIP1-1 was regulated by light period and remarkable higher expression level of BnSIP1-1 was detected in roots than in leaves. Overexpression of BnSIP1-1 in Arabidopsis delayed flowering time for 3–5 days in transgenic plants. In addition, we also found BnSIP1-1 can respond to abiotic and ABA stress (treated with 200 mM NaCl, 300 mM mannitol or 50 μM ABA for 0, 1, 6, and 24 h) in B. napus through adjusting not only ABA but also other endogenous hormones, including indole-3-acetic acid and salicylic acid. Moreover, jasmonates (JA) signaling pathway was found not involving in the pathway of BnSIP1-1 responding to abiotic stresses.

Genome-wide study of pineapple (Ananas comosus L.) bHLH transcription factors indicates that cryptochrome-interacting bHLH2 (AcCIB2) participates in flowering time regulation and abiotic stress response

BackgroundTranscription factors (TFs) are essential regulators of growth and development in eukaryotes. Basic-helix-loop-helix (bHLHs) is one of the most significant TFs families involved in several critical regulatory functions. Cryptochrome-interacting bHLH (CIB) and cryptochromes form an extensive regulatory network to mediate a plethora of pathways. Although bHLHs regulate critical biological processes in plants, the information about pineapple bHLHs remains unexplored.ResultsHere, we identified a total of 121 bHLH proteins in the pineapple genome. The identified genes were renamed based on the ascending order of their gene ID and classified into 18 subgroups by phylogenetic analysis. We found that bHLH genes are expressed in different organs and stages of pineapple development. Furthermore, by the ectopic expression of AcCIB2 in Arabidopsis and complementation of Atcib2 mutant, we verified the involvement of AcCIB2 in photomorphogenesis and abiotic stress response.ConclusionsOur findings revealed that AcCIB2 plays an essential role in flowering time regulation and abiotic stress response. The present study provides additional insights into the current knowledge of bHLH genes and suggests their potential role in various biological processes during pineapple development.

VrLELP controls flowering time under short-day conditions in Arabidopsis.

Flowering time has a critically important effect on the reproduction of plants, and many components involved in flowering-time regulation have been identified in multiple plant species. However, studies of the flowering-time genes in mungbean (Vigna radiata) have been limited. Here, we characterized a novel mungbean gene, VrLELP, involved in flowering-time regulation in transgenic Arabidopsis. Subcellular localization analysis revealed that VrLELP was localized in the membrane, cytoplasm and nucleus and the nucleus and membrane contained higher signal than cytoplasm, similar to the empty vector control. The expression of VrLELP was higher in leaves and pods and lower in nodule roots relative to other tissues. The expression of VrLELP varied during flower development. The expression of VrLELP also varied during the day, reaching a peak after 12h of illumination under long-day conditions. In contrast, under short-day conditions, the abundance of VrLELP transcripts changed little throughout the day. In addition, VrLELP delayed flowering time in transgenic Arabidopsis plants by suppressing the expression of the flowering-time genes CO and FT under short-day conditions. However, VrLELP did not affect flowering time under long-day conditions in Arabidopsis. Our study provides essential information for future studies of the molecular mechanisms of the flowering-time regulation system in mungbean.

Global analysis of CCT family knockout mutants identifies four genes involved in regulating heading date in rice.

Many genes encoding CCT domain-containing proteins regulate flowering time. In rice (Oryza sativa), 41 such genes have been identified, but only a few have been shown to regulate heading date. Here, to test whether and how additional CCT family genes regulate heading date in rice, we classified these genes into five groups based on their diurnal expression patterns. The expression patterns of genes in the same subfamily or in close phylogenetic clades tended to be similar. We generated knockout mutants of the entire gene family via CRISPR/Cas9. The heading dates of knockout mutants of only 4 of 14 genes previously shown to regulate heading date were altered, pointing to functional redundancy of CCT family genes in regulating this trait. Analysis of mutants of four other genes showed that OsCCT22, OsCCT38, and OsCCT41 suppress heading under long-day conditions and promote heading under short-day conditions. OsCCT03 promotes heading under both conditions and upregulates the expression of Hd1 and Ehd1, a phenomenon not previously reported for other such genes. To date, at least 18 CCT domain-containing genes involved in regulating heading have been identified, providing diverse, flexible gene combinations for generating rice varieties with a given heading date.