ZmCCT regulates photoperiod-dependent flowering and response to stresses in maize

Background Appropriate flowering time is very important to the success of modern agriculture. Maize (Zea mays L.) is a major cereal crop, originated in tropical areas, with photoperiod sensitivity. Which is an important obstacle to the utilization of tropical/subtropical germplasm resources in temperate regions. However, the study on the regulation mechanism of photoperiod sensitivity of maize is still in the early stage. Although it has been previously reported that ZmCCT is involved in the photoperiod response and delays maize flowering time under long-day conditions, the underlying mechanism remains unclear. Results Here, we showed that ZmCCT overexpression delays flowering time and confers maize drought tolerance under LD conditions. Implementing the Gal4-LexA/UAS system identified that ZmCCT has a transcriptional inhibitory activity, while the yeast system showed that ZmCCT has a transcriptional activation activity. DAP-Seq analysis and EMSA indicated that ZmCCT mainly binds to promoters containing the novel motifs CAAAAATC and AAATGGTC. DAP-Seq and RNA-Seq analysis showed that ZmCCT could directly repress the expression of ZmPRR5 and ZmCOL9, and promote the expression of ZmRVE6 to delay flowering under long-day conditions. Moreover, we also demonstrated that ZmCCT directly binds to the promoters of ZmHY5, ZmMPK3, ZmVOZ1 and ZmARR16 and promotes the expression of ZmHY5 and ZmMPK3, but represses ZmVOZ1 and ZmARR16 to enhance stress resistance. Additionally, ZmCCT regulates a set of genes associated with plant development. Conclusions ZmCCT has dual functions in regulating maize flowering time and stress response under LD conditions. ZmCCT negatively regulates flowering time and enhances maize drought tolerance under LD conditions. ZmCCT represses most flowering time genes to delay flowering while promotes most stress response genes to enhance stress tolerance. Our data contribute to a comprehensive understanding of the regulatory mechanism of ZmCCT in controlling maize flowering time and stress response.

Characterizing Genetic Mechanisms Involved in Measuring Day-length in Drosophila melanogaster

Many organisms are known to regulate seasonal behaviors and physiological processes in response to day length changes through photoperiodism. Extreme changes in photoperiods have detrimental effects on human health, which can impair development and serve as the origin of adult diseases. Since the seminal work by Bünning in 1936, there are studies supporting the view that organisms can measure the day length through an endogenous 24-hour cellular circadian clock. However, the mechanisms involved in measuring seasonal or day-length changes are not understood. In the current study, we performed a genome-wide association study (GWAS) on photoperiodism using the Drosophila Genetic Reference Panel. The GWAS identified 32 candidate genes responsible for photoperiodic regulations. The knockout mutants of the top four candidate genes (Protein Kinase C delta (Pkcdelta), Glucuronyltransferase-P (GlcAT-P), Brain-specific homeobox (Bsh), and Diuretic hormone 31 Receptor (Dh31-R1)) were analyzed for their photoperiod and circadian period phenotypes. PKCdelta and GlcAT-P mutants show a significantly different photoperiod response compared to that of the wild type strain, and also had an altered circadian period phenotype. Further molecular characterization revealed that the mutant two independent mutant alleles of PKCdelta with a defective catalytic domain had distinct photoperiod responses. Taken these data together, we concluded that there is overlap between the circadian clock and photoperiodic regulations in Drosophila, and PKCdelta is a component that is involved in both circadian and photoperiodic regulations. By identifying novel molecular components of photoperiod, the current study provides new insights into the genetic mechanisms of determining the seasonal changes.

The Winter-Type Allele of HvCEN Is Associated With Earliness Without Severe Yield Penalty in Icelandic Spring Barley (Hordeum vulgare L.)

Icelandic barley genotypes have shown extreme earliness both in flowering and maturity compared to other north European genotypes, whereas earliness is a key trait in adapting barley to northern latitudes. Four genes were partially re-sequenced, which are Ppd-H1, HvCEN, HvELF3, and HvFT1, to better understand the mechanisms underlying this observed earliness. These genes are all known to play a part in the photoperiod response. The objective of this study is to correlate allelic diversity with flowering time and yield data from Icelandic field trials. The resequencing identified two to three alleles at each locus which resulted in 12 haplotype combinations. One haplotype combination containing the winter-type allele of Ppd-H1 correlated with extreme earliness, however, with a severe yield penalty. A winter-type allele in HvCEN in four genotypes correlated with earliness combined with high yield. Our results open the possibility of marker-assisted pyramiding as a rapid way to develop varieties with a shortened time from sowing to flowering under the extreme Icelandic growing conditions and possibly in other arctic or sub-arctic regions.

Structural And Functional Analysis of CCT Family Genes In Pigeonpea

Pigeonpea (Cajanus cajan (L) Millsp) is a short-day plant in which the flowering is highly sensitive to photoperiod. A better understanding of the genes modulating photoresponse and flowering time is critical to developing photoperiod insensitive pigeonpea cultivars for cultivation across the seasons. We identified 33 CCT family genes (CcCCT1- CcCCT33) in C. cajan and localized them on 10 chromosomes and nine genomic scaffolds. The structural analysis of CCT family genes revealed a considerable variation in length and distribution of exons and introns. Based on the type of domain(s), we classified the CCT family genes into CCT motif family (CMF) type, CONSTANS like (COL) type, Pseudo-response Regulator (PRR) type, and GATA and tifi containing CCT (GTCC) type. The CCT family genes of C. cajan exhibited an extensive orthologous relationship with the CCT family genes of other legume species. We also observed significant sharing of CCT family genes among the legume species. Glycine max exhibited the maximum sharing of CCT family genes with C. cajan. The analysis of CCT family proteins-based phylogenic relationships revealed a general congruence with the legumes' taxonomic relationships. The expression analysis of CCT family genes of pigeonpea demonstrated that CcCCT4 and CcCCT23 are the active CONSTANS (CO) in ICP20338. In contrast, only CcCCT23 is active in MAL3, explaining the differential response of ICP20338 and MAL3 to photoperiod. The chromosomes of C. cajan contain a variable number of CCT family genes. A majority of these genes are localized in the centromeric regions. The COL type CCT genes are structurally highly diverse and contain a variable number of B-box domains. The CCT family genes of different legume species exhibit all three kinds of relationships: one-to-one, many-to-one, and many-to-many types. The photoperiod insensitive cultivar ICP20338 contains CcCCT4 and CcCCT23, while the photoperiod sensitive cultivar MAL3 contains only CcCCT23 as active CONSTANS (CO), which may be the plausible reason for their differential photoperiod response.

Dual functions of ZmGI1 in the photoperiodic flowering pathway and salt stress responses in maize

The circadian clock perceives photoperiodic changes and initiates processes leading to floral transition. GIGANTEA (GI) primarily functions as a principal clock component that integrates environmental cues into regulation of growth and development in Arabidopsis. However, it is unclear whether ZmGIs regulate photoperiodic flowering and abiotic stress response. Here, we demonstrated that the expression of ZmGI1 depicted a typical circadian pattern and was differentially expressed under LDs and SDs in photoperiodic sensitive and insensitive maize lines. The transcription level was significantly and positively correlated with days to silking and photoperiodic sensitivity in maize. Moreover, natural variation in ZmGI1 was associated with maize photoperiod response and the fine-tuning of plant development traits. Overexpression of ZmGI1Huangzao4 induced early flowering and enhanced salt tolerance in Arabidopsis relative to the wild-type and gi mutants. ZmGI1 formed a protein complex with ZmFKF1 and acted as a positive regulator of flowering time by regulating CONSTANS transcription in the photoperiod pathway. The ZmGI1/ZmThox complex regulates oxidative stress induced by salt stress via a redox balance pathway. Over all, we have provided compelling evidence to suggest that ZmGI1 is a pleotropic gene whose expression depicts a typical circadian rhythmic pattern and regulates flowering time and confers salt stress tolerance.

Photoperiod induced the pituitary differential regulation of lncRNAs and mRNAs related to reproduction in sheep

The pituitary is a vital endocrine organ that regulates animal seasonal reproduction by controlling the synthesis and secretion of the hormone. The change of photoperiod is the key factor affecting the function of the pituitary in animals, but the mechanism is unclear. Here, we studied the transcriptomic variation in pars distalis (PD) of the pituitary between short photoperiod (SP) and long photoperiod (LP) using RNA sequencing based on the OVX+E2 sheep. 346 differentially expressed (DE) lncRNAs and 186 DE-mRNA were found in the PD. Moreover, function annotation analysis indicated that the reproductive hormones and photoperiod response-related pathways including aldosterone synthesis and secretion, insulin secretion, thyroid hormone synthesis, and circadian entrainment were enriched. The interaction analysis of mRNA-lncRNA suggested that MSTRG.240648, MSTRG.85500, MSTRG.32448, and MSTRG.304959 targeted CREB3L1 and DUSP6, which may be involved in the photoperiodic regulation of the PD. These findings provide resources for further study on the seasonal reproductive in ewes.

Large-Scale Integration of Meta-QTL and Genome-Wide Association Study Discovers the Genomic Regions and Candidate Genes for Yield and Yield-related Traits in Bread Wheat

Improving yield and yield-related traits are key goals in wheat breeding program. The integration of accumulated wheat genetic resources provides an opportunity to uncover important genomic regions and candidate genes that affect wheat yield. Here, a comprehensive Meta-QTL analysis was conducted on 2230 QTLs of yield-related traits obtained from 119 QTL studies. These QTLs were refined into 145 Meta-QTLs (MQTLs), and 89 MQTLs were verified by GWAS with different natural populations. The average confidence interval (CI) of these MQTLs was 2.92 times less than that of the initial QTLs. Furthermore, 76 core MQTL regions with a physical distance less than 25 Mb were detected. Based on the homology analysis and expression patterns, 237 candidate genes in the MQTLs involved in photoperiod response, grain development, multiple plant growth regulator pathways, carbon and nitrogen metabolism, and spike and flower organ development were determined. A novel candidate gene TaKAO-4A was confirmed to be significantly associated with grain size, and a CAPS marker was developed based on its dominant haplotype. In summary, this study clarified a method based on the integration of Meta-QTL, GWAS and homology comparison to reveal the genomic regions and candidate genes that affect important yield-related traits in wheat. This work will help to lay a foundation for the identification, transfer and aggregation of these important QTLs or candidate genes in wheat high-yield breeding.

Assessment of the genetic diversity, population structure and allele distribution of major plant development genes in bread wheat cultivars using DArT and gene-specific markers

Knowledge of the degree of genetic diversity can provide fundamental information to breeders for use in various breeding programmes, for instance for the selection of lines with better adaptability. The genetic diversity analysis of 188 winter wheat genotypes demonstrated that this group of cultivars could be divided into four clusters based primarily on geographical origin. The first group contained mostly American and Asian cultivars, while cluster 2 consisted of Central European cultivars, cluster 3 of Hungarian and South European cultivars and cluster 4 mainly of cultivars from Western Europe. Cultivars used in breeding programmes in Central and South East European breeding programmes were found in all four clusters. Wheat genotypes originating from this region of Europe proved to have greater genetic variability than lines from Western and Northern Europe. Among the four clusters, there were also differencies in the frequencies of winter–spring alleles in Vrn-A1, Vrn-B1, Vrn-D1 vernalisation response genes and in the frequencies of sensitive–insensitive alleles in Ppd-B1 and Ppd-D1 photoperiod response genes, which explained the differences in heading date of the four clusters as well.

Characterization of QTL and Environmental Interactions Controlling Flowering Time in Andean Common Bean (Phaseolus vulgaris L.)

Genetic variation for response of flowering time to photoperiod plays an important role in adaptation to environments with different photoperiods, and as consequence is an important contributor to plant productivity and yield. To elucidate the genetic control of flowering time [days to flowering (DTF); growing degree days (GDD)] in common bean, a facultative short-day plant, a quantitative trait loci (QTL) analysis was performed in a recombinant inbred mapping population derived from a cultivated accession and a photoperiod sensitive landrace, grown in different long-day (LD) and short-day (SD) environments by using a multiple-environment QTL model approach. A total of 37 QTL across 17 chromosome regions and 36 QTL-by-QTL interactions were identified for six traits associated with time to flowering and response to photoperiod. The DTF QTL accounted for 28 and 11% on average of the phenotypic variation in the population across LD and SD environments, respectively. Of these, a genomic region on chromosome 4 harboring the major DTF QTL was associated with both flowering time in LD and photoperiod response traits, controlling more than 60% of phenotypic variance, whereas a major QTL on chromosome 9 explained up to 32% of flowering time phenotypic variation in SD. Different epistatic interactions were found in LD and SD environments, and the presence of significant QTL × environment (QE) and epistasis × environment interactions implies that flowering time control may rely on different genes and genetic pathways under inductive and non-inductive conditions. Here, we report the identification of a novel major locus controlling photoperiod sensitivity on chromosome 4, which might interact with other loci for controlling common bean flowering time and photoperiod response. Our results have also demonstrated the importance of these interactions for flowering time control in common bean, and point to the likely complexity of flowering time pathways. This knowledge will help to identify and develop opportunities for adaptation and breeding of this legume crop.

The apple MdCOP1-interacting protein 1 negatively regulates hypocotyl elongation and anthocyanin biosynthesis

Background In plants, CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) is a key negative regulator in photoperiod response. However, the biological function of COP1-interacting protein 1 (CIP1) and the regulatory mechanism of the CIP1-COP1 interaction are not fully understood. Results Here, we identified the apple MdCIP1 gene based on the Arabidopsis AtCIP1 gene. Expression pattern analysis showed that MdCIP1 was constitutively expressed in various tissues of apple, and responded to stress and hormone signals at the transcriptional level. Ectopic expression of MdCIP1 complemented the phenotypes of the Arabidopsis cip1 mutant, and MdCIP1 inhibited anthocyanin biosynthesis in apple calli. In addition, the biochemical assay demonstrated that MdCIP1 could interact with MdCOP1 protein by their coiled-coil domain, and MdCIP1-OX/cop1–4 had a similar phenotype in photomorphogenesis with the cop1–4 mutant, suggesting that COP1 is epistatic to CIP1. Furthermore, the transient transformation assay indicated that MdCIP1 repressed anthocyanin biosynthesis in an MdCOP1-mediated pathway. Conclusion Take together, this study finds that MdCIP1 acts as a repressor in regulating hypocotyl elongation and anthocyanin biosynthesis through MdCOP1 in apple.