Inheritance of growth habit under photoperiod insensitive genetic background in dolichos bean (Lablab purpureus (L.) Sweet)

Development of high yielding cultivars with determinate growth habit in photoperiod insensitive (PIS) background is one of the major objectives of breeding grain legumes crops including dolichos bean. A thoroughly validated genetic basis is a prerequisite for breeding dolichos bean for determinate growth habit in PIS background. Based on the published reports by researchers of our laboratory and those by others, and our unpublished data, we hypothesized that the number and mode of action of genes controlling growth habit differ with degree of photoperiod sensitivity of the genetic material used to investigate the inheritance of growth habit in dolichos bean. To test this hypothesis, we compared the number and mode of action of genes controlling growth habit between segregating generations in Photoperiod sensitive (PS) and those in PIS genetic backgrounds. While indeterminate and determinate plants segregated in 15:1 ratio in F2 populations derived from crosses between determinate PIS and indeterminate PIS parents, they segregated in 9:7 ratio with indeterminacy being dominant in F2 populations derived from crosses between determinate PIS and indeterminate PS parents. These patterns of segregation (15:1 and 9:7) in favour of indeterminate and determinate plants, respectively in F2 populations were confirmed in F3 populations of PIS and PS genetic backgrounds based on good fit between observed and expected ratios (55:9 and 29:35, respectively) in favour of indeterminate and determinate plants, respectively. The patterns of segregation in F2 populations were further confirmed in F3 populations based on good fit between observed and expected ratios of 3:1 segregating and non-segregating families, and of 3:1 indeterminate and determinate non-segregating families, respectively.

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.

Quantitative Trait Loci and Candidate Genes Associated with Photoperiod Sensitivity in Lettuce (Lactuca spp.)

Key message A population of lettuce that segregated for photoperiod sensitivity was planted under long-day and short-day conditions. Genetic mapping revealed two distinct sets of QTLs controlling daylength-independent and photoperiod-sensitive flowering time. Abstract The molecular mechanism of flowering time regulation in lettuce is of interest to both geneticists and breeders because of the extensive impact of this trait on agricultural production. Lettuce is a facultative long-day plant which changes in flowering time in response to photoperiod. Variations exist in both flowering time and the degree of photoperiod sensitivity among accessions of wild (Lactuca serriola) and cultivated (L. sativa) lettuce. An F6 population of 236 recombinant inbred lines (RILs) was previously developed from a cross between a late-flowering, photoperiod-sensitive L. serriola accession and an early-flowering, photoperiod-insensitive L. sativa accession. This population was planted under long-day (LD) and short-day (SD) conditions in a total of four field and screenhouse trials; the developmental phenotype was scored weekly in each trial. Using genotyping-by-sequencing (GBS) data of the RILs, quantitative trait loci (QTL) mapping revealed five flowering time QTLs that together explained more than 20% of the variation in flowering time under LD conditions. Using two independent statistical models to extract the photoperiod sensitivity phenotype from the LD and SD flowering time data, we identified an additional five QTLs that together explained more than 30% of the variation in photoperiod sensitivity in the population. Orthology and sequence analysis of genes within the nine QTLs revealed potential functional equivalents in the lettuce genome to the key regulators of flowering time and photoperiodism, FD and CONSTANS, respectively, in Arabidopsis.

Quantitative trait loci and candidate genes associated with photoperiod sensitivity in lettuce (Lactuca spp.)

The molecular mechanism of flowering time regulation in lettuce is of interest to both geneticists and breeders because of the extensive impact of this trait on agricultural production. Lettuce is a facultative long-day plant which changes in flowering time in response to photoperiod. Variations exist in both flowering time and the degree of photoperiod sensitivity among accessions of wild (Lactuca serriola) and cultivated (L. sativa) lettuce. An F6 population of 236 recombinant inbred lines (RILs) was previously developed from a cross between a late-flowering, photoperiod-sensitive L. serriola accession and an early-flowering, photoperiod-insensitive L. sativa accession. This population was planted under long-day (LD) and short-day (SD) conditions in a total of four field and screenhouse trials; the developmental phenotype was scored weekly in each trial. Using genotyping-by-sequencing (GBS) data of the RILs, quantitative trait loci (QTL) mapping revealed five flowering time QTLs that together explained more than 20% of the variation in flowering time under LD conditions. Using two independent statistical models to extract the photoperiod sensitivity phenotype from the LD and SD flowering time data, we identified an additional five QTLs that together explained more than 30% of the variation in photoperiod sensitivity in the population. Orthology and sequence analysis of genes within the nine QTLs revealed potential functional equivalents in the lettuce genome to the key regulators of flowering time and photoperiodism, FD and CONSTANS respectively, in Arabidopsis.

Features of modern winter wheat varieties in terms of winter hardiness components under conditions of Ukrainian Forest-Steppe

In recent years, there has been a significant change in climatic conditions affecting the cultivation and yield of winter wheat. Therefore, the creation of wheat varieties with high adaptive potential is one of the main tasks of modern breeding. A significant component of the overall adaptive potential of winter wheat is winter hardiness, which is determined by a set of characters enabling plants to overwinter. To a large extent, winter hardiness is determined by gene systems that control vernalization requirement duration, photoperiod reaction, and frost resistance. The research is aimed at determining the features of modern winter wheat varieties developed at the V. M. Remeslo Myronivka Institute of Wheat of the National Academy of Agrarian Sciences of Ukraine in terms of winter hardiness components and adaptive potential in the environment of the Central part of the Ukrainian Forest-Steppe. Winter bread wheat varieties Estafeta myronivska, Hratsiia myronivska, MIP Assol, and Balada myronivska were studied. They also were crossed on incomplete diallele scheme with three near-isogenic lines derived from Erythrospermum 604 with different alleles of Vrd genes 1) Vrd1Vrd1vrd2vrd2, 2) vrd1vrd1Vrd2Vrd2, and 3) vrd1vrd1vrd2vrd2. It was established that vernalization requirement duration in the varieties Estafeta myronivska and Balada myronivska was short whereas in the varieties Hratsiia myronivska and MIP Assol it was medium. All the varieties studied have medium photoperiod sensitivity. The results of the hybridological analysis indicate the absence of the Vrd1 and Vrd2 genes in the varieties. Frost tolerance of these varieties is at the same level and higher than in the highly tolerant to the low temperatures variety Myronivska 808. Thus, the results indicate the possibility of recombining different levels of expression of these traits in genotypes by breeding efforts. This has great practical importance in farming, because in recent years the areas of crops harvested late (corn, sunflower, etc.) in the production conditions has significantly increased. It causes a shift in sowing dates of winter wheat to a later period. In this case, varieties Estafeta myronivska, Hratsiia myronivska, MIP Assol, and Balada myronivska are able to undergo sufficient hardening, to satisfy the vernalization requirement, and to form a high level of winter hardiness. Their relatively medium photoperiod sensitivity allows vegetation to be restored a little earlier in the spring and winter reserves of moisture to be used more effectively.

Overexpression of a methyl-CpG-binding protein gene OsMBD707 leads to larger tiller angles and reduced photoperiod sensitivity in rice

Background Methyl-CpG-binding domain (MBD) proteins play important roles in epigenetic gene regulation, and have diverse molecular, cellular, and biological functions in plants. MBD proteins have been functionally characterized in various plant species, including Arabidopsis, wheat, maize, and tomato. In rice, 17 sequences were bioinformatically predicted as putative MBD proteins. However, very little is known regarding the function of MBD proteins in rice. Results We explored the expression patterns of the rice OsMBD family genes and identified 13 OsMBDs with active expression in various rice tissues. We further characterized the function of a rice class I MBD protein OsMBD707, and demonstrated that OsMBD707 is constitutively expressed and localized in the nucleus. Transgenic rice overexpressing OsMBD707 displayed larger tiller angles and reduced photoperiod sensitivity—delayed flowering under short day (SD) and early flowering under long day (LD). RNA-seq analysis revealed that overexpression of OsMBD707 led to reduced photoperiod sensitivity in rice and to expression changes in flowering regulator genes in the Ehd1-Hd3a/RFT1 pathway. Conclusion The results of this study suggested that OsMBD707 plays important roles in rice growth and development, and should lead to further studies on the functions of OsMBD proteins in growth, development, or other molecular, cellular, and biological processes in rice.

A critical role of the soybean evening complex in the control of photoperiod sensitivity and adaptation

Photoperiod sensitivity is a key factor in plant adaptation and crop production. In the short-day plant soybean, adaptation to low latitude environments is provided by mutations at the J locus, which confer extended flowering phase and thereby improve yield. The identity of J as an ortholog of Arabidopsis ELF3, a component of the circadian evening complex (EC), implies that orthologs of other EC components may have similar roles. Here we show that the two soybean homeologs of LUX ARRYTHMO interact with J to form a soybean EC. Characterization of mutants reveals that these genes are highly redundant in function but together are critical for flowering under short day, where the lux1 lux2 double mutant shows extremely late flowering and a massively extended flowering phase. This phenotype exceeds that of any soybean flowering mutant reported to date, and is strongly reminiscent of the “Maryland Mammoth” tobacco mutant that featured in the seminal 1920 study of plant photoperiodism by Garner and Allard [W. W. Garner, H. A. Allard, J. Agric. Res. 18, 553–606 (1920)]. We further demonstrate that the J–LUX complex suppresses transcription of the key flowering repressor E1 and its two homologs via LUX binding sites in their promoters. These results indicate that the EC–E1 interaction has a central role in soybean photoperiod sensitivity, a phenomenon also first described by Garner and Allard. EC and E1 family genes may therefore constitute key targets for customized breeding of soybean varieties with precise flowering time adaptation, either by introgression of natural variation or generation of new mutants by gene editing.

The Effect of Photoperiod Genes and Flowering Time on Yield and Yield Stability in Durum Wheat

This study analysed the effect of flowering time as influenced by photoperiod sensitivity genes on yield and yield stability in durum wheat. Twenty-three spring genotypes harbouring different allele combinations at Ppd-A1 and Ppd-B1 were grown in 15 field experiments at three sites at latitudes from 41° to 19° N (Spain, Mexico-North and Mexico-South). Low temperature and solar radiation before flowering and long day length during grain-filling characteristic for the Spanish site resulted in high grain number/m2 (GN) and yield (GY), while a moderate GN combined with high solar radiation during grain-filling at Mexico-North led to heavier grains. Allele combination GS100-Ppd-A1a/Ppd-B1a reduced the flowering time up to nine days when compared with Ppd-A1b/Ppd-B1a. Differences in flowering time caused by Ppd-A1/Ppd-B1 allele combinations did not affect yield. Combinations GS105-Ppd-A1a/Ppd-B1b and Ppd-A1b/Ppd-B1b resulted in the highest GN, linked to spikelets/spike, which was higher in GS105-Ppd-A1a/Ppd-B1b due to more grains/spikelet. Flowering time caused by Eps had a minor effect on GN, spikes/m2 and grains/spike, but late flowering resulted in reduced grain weight and GY. Allele combinations harbouring alleles conferring a similar photoperiod sensitivity response at Ppd-A1 and Ppd-B1 resulted in greater yield stability than combinations that carry alleles conferring a different response. Allele combination GS100-Ppd-A1a/Ppd-B1a was the most suitable in terms of yield and yield stability of durum wheat cultivated under irrigation within the studied latitudes.

Overexpression of a methyl-CpG-binding Protein Gene OsMBD707, Leads to Larger Tiller Angles and Reduced Photoperiod Sensitivity in Rice

Background: Methyl-CpG-binding domain (MBD) proteins play important roles in epigenetic gene regulation, and have diverse molecular, cellular, and biological functions in plants. MBD proteins have been functionally characterized in various plant species, including Arabidopsis, wheat, maize, and tomato. In rice, 17 sequences were bioinformatically predicted as putative MBD proteins. However, very little is known regarding the function of MBD proteins in rice.Results: We explored the expression patterns of the rice OsMBD family genes and identified 13 OsMBDs with active expression in various rice tissues. We further characterized the function of a rice class I MBD protein OsMBD707, and demonstrated that OsMBD707 is constitutively expressed and localized in the nucleus. Transgenic rice overexpressing OsMBD707 displayed larger tiller angles and reduced photoperiod sensitivity—delayed flowering under short day (SD) and early flowering under long day (LD). RNA-seq analysis revealed that overexpression of OsMBD707 led to reduced photoperiod sensitivity in rice through regulating expression of key flowering regulator genes in the Ehd1-Hd3a/RFT1 pathway.Conclusion: The results of this study demonstrated that OsMBD707 plays important roles in rice growth and development, and should lead to further studies on the functions of OsMBD proteins in growth, development, or other molecular, cellular, and biological processes in rice.