Early Flowering Time Research Articles

The immunophilin CYCLOPHILIN28 affects PSII-LHCII supercomplex assembly and accumulation in Arabidopsis thaliana.

In plant chloroplasts, photosystem II (PSII) complexes, together with light-harvesting complex II (LHCII), form various PSII-LHCII supercomplexes (SCs). This process likely involves immunophilins, but the underlying regulatory mechanisms are unclear. Here, by comparing Arabidopsis thaliana mutants lacking the chloroplast lumen-localized immunophilin CYCLOPHILIN28 (CYP28) to wild-type and transgenic complemented lines, we determined that CYP28 regulates the assembly and accumulation of PSII-LHCII SCs. Compared to the wild type, cyp28 plants showed accelerated leaf growth, earlier flowering time, and enhanced accumulation of high molecular weight PSII-LHCII SCs under normal light conditions. The lack of CYP28 also significantly affected the electron transport rate. Blue native-polyacrylamide gel electrophoresis analysis revealed more Lhcb6 and less Lhcb4 in M-LHCII-Lhcb4-Lhcb6 complexes in cyp28 versus wild-type plants. Peptidyl-prolyl cis/trans isomerase (PPIase) activity assays revealed that CYP28 exhibits weak PPIase activity and that its K113 and E187 residues are critical for this activity. Mutant analysis suggested that CYP28 may regulate PSII-LHCII SC accumulation by altering the configuration of Lhcb6 via its PPIase activity. Furthermore, the Lhcb6-P139 residue is critical for PSII-LHCII SC assembly and accumulation. Therefore, our findings suggest that CYP28 likely regulates PSII-LHCII SC assembly and accumulation by altering the configuration of P139 of Lhcb6 via its PPIase activity.

Phenotypic differentiation and diversifying selection in populations of Eruca sativa along an aridity gradient

BackgroundThe aridity gradient in the eastern Mediterranean offers an opportunity to investigate intra-specific genetic differentiation and local adaptation in plant populations. Here we used genetic (FST) and quantitative trait (PST) differentiation to assess local adaptation among three natural populations of Eruca sativa (Brassicaceae) distributed along a climatic range representing desert, semi-arid and Mediterranean habitats.ResultsAmplified fragment length polymorphism (AFLP) analysis revealed high genetic diversity in each population, but low genetic differentiation between populations and relatively high gene flow. Further phenotypic evaluation in a common garden experiment (conduced in a Mediterranean habitat) showed clear differences in phenological traits among populations (day of flowering and duration of the reproductive stage), shoot and root biomass, as well as fitness-related traits (total number of fruits and total seed weight). FST–PST comparison showed that PST values of the phenological traits, as well as below- and above-ground biomass and fitness-related traits, were higher than the FST values.ConclusionsOverall, our results support the identification of genotypic and phenotypic differentiation among populations of E. sativa. Furthermore, the FST–PST comparison supports the hypothesis that these were subjected to past diversifying selection. Thus, the results clearly demonstrate adaptive divergence among populations along an aridity gradient, emphasize the ecological value of early flowering time in arid habitats, and contribute to our understanding of the possible impact of climate change on evolutionary processes in plant populations.

Evaluation of Seed Yield and Yield Components of Some Chickpea Genotopes Grown under Şirnak-Idil Ecological Conditions

This study was carried out to determine the yield and yield factors of some chickpea genotypes in Şırnak-İdil ecological conditions. In the research, 12 lines and 4 control cultivars (Arda, Azkan, Aksu and Inci) totally 15 chickpea genotypes were used as material. Field experiment was carried out in Sirnak-Idil conditions, in the cultivation period (Novevember-July) of 2020/2021, in a randomized block design with three replications. As a result of the research, although it varies according to chickpea genotypes, the number of days until flowering, average plant height, first pod height, the number of branches, the number of pods, the number of grains, grain weight, grain yield, hundred grain weight, harvest index value varied between 115.7 and 161.7 days, between 42.9 cm and 53.5 cm, between 15.2 cm and 26.2 cm, between 2.0 and 3.9, between 23.0 and 43.4, between 14.0 and 44.0, between 9.2 and 13.4 g, between 98.4 and 160.7 kg da-1, between 23.3 and 37.6 g, 34.5 and 46.2%, respectively. As a result, in Sirnak/Idil ecological condition, FLIP 03-104 C chickpea genotype can give better results in arid and semiarid conditions because of its early flowering and podding time; It was determined that Arda and FLIP 97-503 C chickpea genotypes gave better results than other genotypes examined in terms of yield and yield-related characteristics.

Evolution of flowering time in a selfing annual plant: Roles of adaptation and genetic drift.

Resurrection studies are a useful tool to measure how phenotypic traits have changed in populations through time. If these trait modifications correlate with the environmental changes that occurred during the time period, it suggests that the phenotypic changes could be a response to selection. Selfing, through its reduction of effective size, could challenge the ability of a population to adapt to environmental changes. Here, we used a resurrection study to test for adaptation in a selfing population of Medicago truncatula, by comparing the genetic composition and flowering times across 22 generations. We found evidence for evolution toward earlier flowering times by about two days and a peculiar genetic structure, typical of highly selfing populations, where some multilocus genotypes (MLGs) are persistent through time. We used the change in frequency of the MLGs through time as a multilocus fitness measure and built a selection gradient that suggests evolution toward earlier flowering times. Yet, a simulation model revealed that the observed change in flowering time could be explained by drift alone, provided the effective size of the population is small enough (<150). These analyses suffer from the difficulty to estimate the effective size in a highly selfing population, where effective recombination is severely reduced.

Cover Image, Volume 16, Issue 1

On the cover: Researcher Teclemariam Weldekidan in front of a series of two‐row plots of selected generations from the tropical synthetic of maize (the Delaware lineage). See T. Weldekidan et al., “Registration of tropical populations of maize selected in parallel for early flowering time across the United States,” https://doi.org/10.1002/plr2.20181. Photo by University of Delaware. image

RNAi silencing of the Arabidopsis thaliana ULCS1 gene results in pleiotropic phenotypes during plant growth and development.

WD40-repeat-containing proteins (WDRs) are highly abundant in all eukaryotes. Several have been implicated as subunits of multi-protein CRL E3 ligase complexes that regulate ubiquitination mediated protein degradation and thus various cellular and developmental processes. Impairment of the WDR protein ULCS1 from Arabidopsis causes pleiotropic phenotypes during plant development, including reduced lignification, anther indehiscence, and sterility. Here we show that RNAi-mediated downregulation of ULCS1 results in a fast-growing phenotype during vegetative development. Due to accelerated growth, ulcs1i mutants reach their vegetative to reproductive transition point earlier than WT plants. However, their comparable germination rate and their similar number of secondary branches and rosette leaves at bolting indicate that ulcs1i is not an early flowering time mutant. GUS staining of progeny, obtained from crosses between ulcs1i and CYCB1::GUS plants, revealed an increased number of mitotic cell divisions in the root meristems of ulcs1i compared to WT. Immunolabeling of homogalacturonans (HGAs) epitopes showed significant fluorescent signal differences at the cell walls and the mucilage of the seeds between ulcs1i and WT. Furthermore, we demonstrate that ULCS1 interacts with the UBA-like protein in a yeast two-hybrid assay, suggesting a direct or indirect physical coupling of these proteins in Arabidopsis.

Altered H3K27 trimethylation contributes to flowering time variations in polyploid Arabidopsis thaliana ecotypes.

Polyploidy is a widespread phenomenon in flowering plant species. Polyploid plants frequently exhibit considerable transcriptomic alterations after whole-genome duplication (WGD). It is known that the transcriptomic response to tetraploidization is ecotype-dependent in Arabidopsis; however, the biological significance and the underlying mechanisms are unknown. In this study, we found that 4x Col-0 presents a delayed flowering time whereas 4x Ler does not. The expression of FLOWERING LOCUS C (FLC), the major repressor of flowering, was significantly increased in 4x Col-0 but only a subtle change was present in 4x Ler. Moreover, the level of a repressive epigenetic mark, trimethylation of histone H3 at lysine 27 (H3K27me3), was significantly decreased in 4x Col-0 but not in 4x Ler, potentially leading to the differences in FLC transcription levels and flowering times. Hundreds of other genes in addition to FLC showed H3K27me3 alterations in 4x Col-0 and 4x Ler. LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) and transcription factors required for H3K27me3 deposition presented transcriptional changes between the two ecotypes, potentially accounting for the different H3K27me3 alterations. We also found that the natural 4x Arabidopsis ecotype Wa-1 presented an early flowering time, which was associated with low expression of FLC. Taken together, our results demonstrate a role of H3K27me3 alterations in response to genome duplication in Arabidopsis autopolyploids, and that variation in flowering time potentially functions in autopolyploid speciation.

Registration of tropical populations of maize selected in parallel for early flowering time across the United States

AbstractTropical strains of maize (Zea mays subsp. mays L.) flower very late in temperate environments. This is a barrier to maize diversification and improvement in regions where a large share of the world's corn production takes place. For investigating early flowering time adaptation, a tightly controlled parallel selection experiment spanning a 28° latitudinal range (∼3,100 km) across the United States was conducted. First, a tropical synthetic population (TropicS‐G0) (Reg. no. GP‐605, PI 698625) of maize was created from seven inbred parents. The molecular genetic diversity in TropicS‐G0 is representative of tropical inbreds that are differentiated from the prevailing germplasm used for hybrid production in the United States. Admixture analysis and genome simulation showed that breeding of TropicS‐G0 captured the parental genomes mostly at random, as intended prior to selection. With TropicS‐G0 as a common base population, a standardized protocol was used to recurrently select for early flowering time at eight locations for two generations, giving rise to location‐specific lineages (TropicS‐G1‐PR, Reg. no. GP‐621, PI 698641; TropicS‐G2‐PR, Reg. no. GP‐622, PI 698642; TropicS‐G2‐FL, Reg. no. GP‐620, PI 698640; TropicS‐G1‐cTX, Reg. no. GP‐618, PI 698638; TropicS‐G2‐cTX, Reg. no. GP‐619, PI 698639; TropicS‐G1‐nTX, Reg. no. GP‐616, PI 698636; TropicS‐G2‐nTX, Reg. no. GP‐617, PI 698637; TropicS‐G1‐NC, Reg. no. GP‐614, PI 698634; TropicS‐G2‐NC, Reg. no. GP‐615, PI 698635; TropicS‐G1‐DE, Reg. no. GP‐610, PI 698630; TropicS‐G1‐IA, Reg. no. GP‐608, PI 698628; TropicS‐G2‐IA, Reg. no. GP‐609, PI 698629; TropicS‐G1‐WI, Reg. no. GP‐606, PI 698626; TropicS‐G2‐WI, Reg. no. GP‐607, PI 698627). Additional generations of selection were performed for the DE lineage (TropicS‐G3‐DE, Reg. no. GP‐611, PI 698631; TropicS‐G4‐DE, Reg. no. GP‐612, PI 698632; TropicS‐G5‐DE, Reg. no. GP‐613, PI 698633). The parallel‐selected maize population is a novel resource for breeders and those seeking to investigate adaptation.

Comprehensive Analysis of Five Phyllostachys edulisSQUA-like Genes and Their Potential Functions in Flower Development.

Bamboo is one of the most important non-timber forest resources worldwide. It has considerable economic value and unique flowering characteristics. The long juvenile phase in bamboo and unpredictable flowering time limit breeding and genetic improvement and seriously affect the productivity and application of bamboo forests. Members of SQUA-like subfamily genes play an essential role in controlling flowering time and floral organ identity. A comprehensive study was conducted to explain the functions of five SQUA-like subfamily genes in Phyllostachys edulis. Expression analysis revealed that all PeSQUAs have higher transcript levels in the reproductive period than in the juvenile phase. However, PeSQUAs showed divergent expression patterns during inflorescence development. The protein–protein interaction (PPI) patterns among PeSQUAs and other MADS-box members were analyzed by yeast two-hybrid (Y2H) experiments. Consistent with amino acid sequence similarity and phylogenetic analysis, the PPI patterns clustered into two groups. PeMADS2, 13, and 41 interacted with multiple PeMADS proteins, whereas PeMADS3 and 28 hardly interacted with other proteins. Based on our results, PeSQUA might possess different functions by forming protein complexes with other MADS-box proteins at different flowering stages. Furthermore, we chose PeMADS2 for functional analysis. Ectopic expression of PeMADS2 in Arabidopsis and rice caused early flowering, and abnormal phenotype was observed in transgenic Arabidopsis lines. RNA-seq analysis indicated that PeMADS2 integrated multiple pathways regulating floral transition to trigger early flowering time in rice. This function might be due to the interaction between PeMADS2 and homologous in rice. Therefore, we concluded that the five SQUA-like genes showed functional conservation and divergence based on sequence differences and were involved in floral transitions by forming protein complexes in P. edulis. The MADS-box protein complex model obtained in the current study will provide crucial insights into the molecular mechanisms of bamboo’s unique flowering characteristics.

Comparison of feed value of Amaranthus powellii Willd. forage to some roughage feeds

The aim of this study was to compare the chemical composition, in vitro digestibility, protein and energy value, roughage value of Amaranthus powellii Willd. forage to the most commonly used alfalfa hay and wheat straw in ruminant nutrition. Amaranthus powellii Willd. forage has the potential to be a third quality roughage according to its relative feed value assessment of 104.55 ± 0.67. In addition, the relative forage quality assessment developed for feeding dairy cattle was 97.73 ± 0.05 for Amaranthus powellii Willd. forage, which had a higher the relative forage quality value than alfalfa hay and wheat straw, and it can be used for feeding dairy or fattening cattle. However, it has been generally recommended that Amaranth be given either by grazing at its early flowering time or via silage due to the oxalic acid and nitrate salts. Amaranthus powellii Willd. forage should also be determined nitrate, amino acids, and other antinutritional factors before studied in vivo as hay or silage.

Integrative analysis of GWAS and transcriptome to reveal novel loci regulation flowering time in semi-winter rapeseed

Flowering is an important turning point from vegetative growth to reproductive growth, and vernalization is an essential condition for the flowering of annual winter plants. To investigate the genetic architecture of flowering time in rapeseed, we used the 60 K Brassica Infinium SNP array to perform a genome-wide analysis of haplotype blocks associated with flowering time in 203 Chinese semi-winter rapeseed inbred lines. Twenty-one haplotype regions carrying one or more candidate genes showed a significant association with flowering time. Interestingly, we detected a SNP (Bn-scaff_22728_1-p285715) located in exon 3 of the BnVIN3-C03 gene that showed a significant association with flowering time on chromosome C03. Based on the SNP alleles A and G, two groups of accessions with early and late flowering time phenotypes were selected, respectively, and PCR amplification and gene expression analysis were combined to reveal the structural variation of the BnVIN3-C03 gene that affected flowering time. Moreover, we found that BnVIN3-C03 inhibited the expression of BnFLC-A02, BnFLC-A03.1, BnFLC-A10 and BnFLC-C03.1, thus modulating the flowering time of Brassica napus. This result provides insight into the genetic improvement of flowering time in B. napus.

Divergent shifts in flowering phenology of herbaceous plants on the warming Qinghai–Tibetan plateau

Both advanced and delayed shifts of different magnitude in flowering phenology, based on limited controlled experiments and ground-based observational studies, have been reported on the Qinghai–Tibetan Plateau (QTP). To clarify flowering phenological changes, we collected 1646 ground-observed phenological records of 21 species, from 27 stations, for 78 time series, and daily average air temperature data from 1983 to 2017 on the QTP. Trends in the first flowering date (FFD) and changes with temperature increase were analyzed using regression models. The FFD of early flowering time series showed an overall trend for significant advance (-0.371 ± 0.149 days/year, p < 0.001), whereas the mid-to-late-flowering showed a delayed trend (0.158 ± 0.193 days/year, p = 0.108). This finding is in contrast with the stable trend for early flowering species and the advanced trend for midsummer and late-flowering species in high latitude and Arctic regions, where the low-temperature environment is similar. The growing degree days from 1 January to the day of the observed occurrence of the FFD for early flowering time series kept stable (p = 0.531) and FFD showed a positive regression with chilling days; however, the growing degree days of mid-to-late-flowering time series increased significantly at a rate of 5.375 ± 2.519°C-days/year (p < 0.001), indicating the limitation on FFD from other related climatic factors except for forcing temperature may strengthen, and FFD showed no relationship with chilling days. The mid-to-late-flowering time series showed vernalization sensitivity in the spring of the flowering year, whereas the early flowering time series did not. This indicated that retarded vernalization completion may be responsible for the delayed flowering phenology of mid-to-late-flowering species. The FFD of early flowering species, with flower preformation in the preceding autumn, was mainly controlled by forcing temperature in spring; decreased chilling days indicating warmer winter were also beneficial for development and fitness of preformed floral organs, and thus, temperature increase significantly advanced the FFD. These findings suggest that divergent flowering phenology shifts may alter the species composition and ecosystem services of alpine ecosystems, causing challenges in grassland management.

GmRAV confers ecological adaptation through photoperiod control of flowering time and maturity in soybean.

Photoperiod strictly controls vegetative and reproductive growth stages in soybean (Glycine max). A soybean GmRAV (Related to ABI3/VP1) transcription factor containing both AP2 and B3 domains was shown to be a key component of this process. We identified six polymorphisms in the GmRAV promoter that showed significant association with flowering time and maturity of soybean in one or multiple environments. Soybean varieties with minor polymorphism exhibited a longer growth period contributing to soybean adaptation to lower latitudes. The cis-acting element GT1CONSENSUS motif of the GmRAV promoter controlled the growth period, and the major allele in this motif shortened duration of late reproductive stages by reducing GmRAV expression levels. Three GmRAV-overexpressing (GmRAV-ox) transgenic lines displayed later flowering time and maturity, shorter height and fewer numbers of leaves compared with control plants, whereas transgenic inhibition of GmRAV expression resulted in earlier flowering time and maturity and increased plant height. Combining DNA affinity purification sequencing and RNA sequencing analyses revealed 154 putative target genes directly bound and transcriptionally regulated by GmRAV. Two GmRAV binding motifs [C(A/G)AACAA(G/T)A(C/T)A(G/T)] and [C(T/A)A(C)C(T/G)CTG] were identified, and acting downstream of E3E4, GmRAV repressed GmFT5a transcriptional activity through binding a CAACA motif, thereby delaying soybean growth and extending both vegetative and reproductive phases.

The adaptive value of flowering time in wild radish (Raphanus raphanistrum)

AbstractHarvest weed seed control (HWSC) is a weed management technique that intercepts and destroys weed seeds before they replenish the soil weed seedbank and can be used to control herbicide-resistant weeds in global cropping systems. Wild radish (Raphanus raphanistrum L.) is a problematic, globally distributed weed species that is considered highly susceptible to HWSC, as it retains much of its seed on the plant during grain harvest. However, previous studies have demonstrated that R. raphanistrum is capable of adapting its life cycle, in particular its flowering time, to allow individuals more time to mature and potentially shed seeds before harvest, thereby evading HWSC interception. This study compared the vegetative growth plus physiological and ecological fitness of an early-flowering R. raphanistrum biotype with an unselected genetically related biotype to determine whether physiological costs of early flowering exist when in competition with wheat (Triticum aestivum L.). Early flowering time adaptation in R. raphanistrum did not change the relative growth rate or competitive ability of R. raphanistrum. However, the height of first flower was reduced in the early flowering time–selected population, indicating that this population would retain more pods below the typical harvest cutting height (15 cm) used in HWSC. The presence of wheat competition (160 to 200 plants m−2) increased flowering height in the early flowering time–selected population, which would likely increase the susceptibility of early-flowering R. raphanistrum plants to HWSC. Overall, early-flowering adaption in R. raphanistrum is a possible strategy to escape being captured by the HWSC; however, increasing crop competition is likely to be an effective strategy to maintain the effectiveness of HWSC.

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.

Identification of early and late flowering time candidate genes in endodormant and ecodormant almond flower buds.

Flower bud dormancy in temperate fruit tree species, such as almond [Prunus dulcis (Mill.) D.A. Webb], is a survival mechanism that ensures that flowering will occur under suitable weather conditions for successful flower development, pollination and fruit set. Dormancy is divided into three sequential phases: paradormancy, endodormancy and ecodormancy. During the winter, buds need cultivar-specific chilling requirements (CRs) to overcome endodormancy and heat requirements to activate the machinery to flower in the ecodormancy phase. One of the main factors that enables the transition from endodormancy to ecodormancy is transcriptome reprogramming. In this work, we therefore monitored three almond cultivars with different CRs and flowering times by RNA sequencing during the endodormancy release of flower buds and validated the data by quantitative real-time PCR in two consecutive seasons. We were thus able to identify early and late flowering time candidate genes in endodormant and ecodormant almond flower buds associated with metabolic switches, transmembrane transport, cell wall remodeling, phytohormone signaling and pollen development. These candidate genes were indeed involved in the overcoming of the endodormancy in almond. This information may be used for the development of dormancy molecular markers, increasing the efficiency of temperate fruit tree breeding programs in a climate-change context.

Adaptive genetic potential and plasticity of trait variation in the foundation prairie grass Andropogon gerardii across the US Great Plains' climate gradient: Implications for climate change and restoration.

Plant response to climate depends on a species’ adaptive potential. To address this, we used reciprocal gardens to detect genetic and environmental plasticity effects on phenotypic variation and combined with genetic analyses. Four reciprocal garden sites were planted with three regional ecotypes of Andropogon gerardii, a dominant Great Plains prairie grass, using dry, mesic, and wet ecotypes originating from western KS to Illinois that span 500–1,200 mm rainfall/year. We aimed to answer: (a) What is the relative role of genetic constraints and phenotypic plasticity in controlling phenotypes? (b) When planted in the homesite, is there a trait syndrome for each ecotype? (c) How are genotypes and phenotypes structured by climate? and (d) What are implications of these results for response to climate change and use of ecotypes for restoration? Surprisingly, we did not detect consistent local adaptation. Rather, we detected co‐gradient variation primarily for most vegetative responses. All ecotypes were stunted in western KS. Eastward, the wet ecotype was increasingly robust relative to other ecotypes. In contrast, fitness showed evidence for local adaptation in wet and dry ecotypes with wet and mesic ecotypes producing little seed in western KS. Earlier flowering time in the dry ecotype suggests adaptation to end of season drought. Considering ecotype traits in homesite, the dry ecotype was characterized by reduced canopy area and diameter, short plants, and low vegetative biomass and putatively adapted to water limitation. The wet ecotype was robust, tall with high biomass, and wide leaves putatively adapted for the highly competitive, light‐limited Eastern Great Plains. Ecotype differentiation was supported by random forest classification and PCA. We detected genetic differentiation and outlier genes associated with primarily precipitation. We identified candidate gene GA1 for which allele frequency associated with plant height. Sourcing of climate adapted ecotypes should be considered for restoration.

Genome-wide characterization of the SPL gene family involved in the age development of Jatropha curcas

BackgroundSPL (SQUAMOSA-promoter binding protein-like) proteins form a large family of plant-specific transcription factors that play essential roles in various aspects of plant growth and development. They are potentially important candidates for genetic improvement of agronomic traits. However, there were limited information about the SPL genes in Jatropha curcas, an important biofuel plant.ResultsIn Jatropha, 15 JcSPL genes were identified. Phylogenetic analysis revealed that most of the JcSPLs were closely related to SPLs from woody plant rather than herbaceous plant and distantly related to monocotyledon SPLs. Gene structure, conserved motif and repetitive sequence analysis indicated diverse and specific functions of some JcSPL genes. By combination of target prediction and degradome sequencing analysis, 10 of the 15 JcSPLs were shown to be targets of JcmiR156. Quantitative PCR analysis showed diversified spatial-temporal expression patterns of JcSPLs. It is interesting that the expression levels of JcSPL3 were the highest in all tissues examined in 7- or 10-year-old plants and exhibited increasing trend with plant age, suggesting its important role in the regulation of age development in Jatropha. Overexpression of JcSPL3 in Arabidopsis resulted in earlier flowering time, shorter silique length and reduced biomass of roots.ConclusionsThrough comprehensive and systematic analysis of phylogenetic relationships, conserved motifs, gene structures, chromosomal locations, repetitive sequence and expression patterns, 15 JcSPL genes were identified in Jatropha and characterized in great detail. These results provide deep insight into the evolutionary origin and biological significance of plant SPLs and lay the foundation for further functional characterization of JcSPLs with the purpose of genetic improvement in Jatropha.

Ectopic expression of a R2R3 MYB transcription factor of dove tree (Davidia involucrata) aggravates seed abortion in Arabidopsis thaliana.

Serious seed abortion of dove tree (Davidia involucrate Baill.) is one of the critical factors leading to the low fecundity of this species. Seed abortion is a complicated process and various factors have been verified to synergistically determine the fate of seeds. To reveal the mechanism of seed abortion in D. involucrata, we performed transcriptome analysis in normal and abortive seeds of D. involucrata. According to the transcriptome data, we noticed that most of the genes encoding a MYB transcription factor were predominantly expressed in abortive seeds. Among these, a gene named DiMYB1 was selected and its function was validated in this study. Overexpression of DiMYB1 resulted in obviously reduced viability of transgenic seeds and seedlings, and caused a significantly higher seed abortion rate. The vegetative growth of transgenic plants was hindered, resulting in an earlier flowering time. In addition, colour changes occurred in transgenic plants. Some transgenic sprouts, stems and pods appeared purple instead of green in colour. Our finding demonstrated that DiMYB1 participates in multiple plant developmental processes, especially in seed development in Arabidopsis thaliana (L.) Heynh., which indicated the similar role of this gene in D. involucrata.

A novel genotype DATTO5 developed using the five genes exhibits the fastest heading date designed in rice.

The optimization of heading date is a key aspect for maximizing grain productivity in cereal crops including rice. The combinations of genes for heading date, a quantitative trait, are a major driver in the wide adaptability of cultivated rice worldwide. Here, we identified a novel QTL, qDTH3 (quantitative trait locus for days-to-heading on chromosome 3), for early flowering time in the F2 population derived from a cross between Hoshinoyume (HS) and Daichinohoshi (DH) among local rice populations with extremely early heading date. The DH allele at qDTH3, qDTH3DH, headed 2.7 days earlier than the HS allele at qDTH3, qDTH3HS. We sought to design a genotype for earlier heading date by pyramiding of five heading date genes. We designated this aggregate of the five genes as DATTO5. Plants with DATTO5 were selected from the F2 population derived from a cross between DH and HShd5, which is a near-isogenic line carrying a loss-of-function of days to heading 8 in a genetic background of HS. Plants with DATTO5 exhibited earlier heading date but reduced fitness, including shorter culm and panicle length and fewer seeds compared with HS, as a representative local rice variety with extremely early heading date.