Long-day Conditions Research Articles

Soybean WRINKLED1 protein GmWRI1a promotes flowering under long-day conditions via regulating expressions of flowering-related genes

Flowering time is an important agronomic character that influences the adaptability and yield of soybean [Glycine max (L.) Merrill]. WRINKLED 1 (WRI1) plays an important regulatory role in plant growth and development. In this study, we found that the expression of GmWIR1a could be induced by long days. Compared with the wild type, transgenic soybean overexpressing GmWRI1a showed earlier flowering and maturity under long days but no significant changes under short days. Overexpression of GmWRI1a led to up-regulated expression of genes involved in the regulation of flowering time. The GmWRI1a protein was able to directly bind to the promoter regions of GmAP1, GmFUL1a, GmFUL2 and up-regulated their expression. GmCOL3 was identified by yeast one-hybrid library screening using the GmWRI1a promoter as bait. GmCOL3 was revealed to be a nucleus-localized protein that represses the transcription of GmWRI1a. Expression of GmCOL3 was induced by short days. Taken together, the results show that overexpression of GmWRI1a promotes flowering under long days by promoting the transcriptional activity of flowering-related genes in soybean, and that GmCOL3 binds to the GmWRI1a promoter and directly down-regulates its transcription. This discovery reveals a new function for GmWRI1a, which regulates flowering and maturity in soybean.

Field Screening of Diverse Soybean Germplasm to Characterize Their Adaptability under Long-Day Condition

Soybean is a short-day crop, and its sensitivity to photoperiod is an important trait for its adaptability. Rapid changes in the climate on a global scale could be a threat to future food security. There is a need to increase the heat tolerance of soybean to sustain its production. The availability of global germplasm provides plant breeders with the opportunity to explore the genetic potential of the existing soybean germplasm. For this purpose, a panel of 203 soybean accessions from different global climatic zones was evaluated for adaptability under long-day conditions. Field screening of the soybean germplasm was conducted over two consecutive years, 2016 and 2017, in Faisalabad, Pakistan. This study screened 15 diverse soybean accessions that exhibited economically viable yields in both years, i.e., 1500–2200 kg/ha. Data related to plant height, node number, pods per plant, seeds per plant, seed weight per plant, hundred-grain weight, and total yield were recorded. Two soybean accessions, PI548271 (MG-IV) and PI553039 (MG-IV,) produced the highest yield in both years. The genotypic and phenotypic coefficients of variance, broad-sense heritability, and genetic advances observed in their yields were also high. These results highlight the potential pre-existing genetic variation required to improve the adaptation of soybean to long-day conditions. Some of the accessions identified in the current study could be recommended for general cultivation under long-day and high-temperature conditions.

The influence of bacterization on the formation of the crop structure of soybean isogenic lines by E-genes in conditions of different photoperiod

Aim. To study the effect of treatment with the Bradyrhizobium japonicum 634b strain on the formation of the crop structure of soybean lines isogenic by photoperiodic sensitivity control genes, under conditions of long and short days. Methods. The experiment was done in the field. After sterilization, the seeds were treated with Bradyrhizobium japonicum 634b and planted in the soil; control test - seeds treated with distilled water. Plants were grown under natural long day conditions (16 h), in phase V3 the experimental plants were exposed to (artificially created) short day (9 h) for two weeks. The elements of the crop structure were analyzed. Results. In the short day condition and bacterization, we observe a significant decrease in the shoot length, the number of pods and seeds in short-day lines, and at the same time a significant increase in the indicators in long-day lines. In the long day condition, we observe more complex regularities, which, we assume, are associated with a closer and more specific interaction between the plant genotype and microorganisms. Conclusions. It was revealed that the genotype and its interaction with the bacterization factor has the greatest influence on the studied indicators, both under short and long day conditions.

The WD40 domain-containing protein Ehd5 positively regulates flowering in rice (Oryza sativa).

Heading date (flowering time), which greatly influences regional and seasonal adaptability in rice (Oryza sativa), is regulated by many genes in different photoperiod pathways. Here, we characterized a heading date gene, Early heading date 5 (Ehd5), using a modified bulked segregant analysis method. The ehd5 mutant showed late flowering under both short-day and long-day conditions, as well as reduced yield, compared to the wild type. Ehd5, which encodes a WD40 domain-containing protein, is induced by light and follows a circadian rhythm expression pattern. Transcriptome analysis revealed that Ehd5 acts upstream of the flowering genes Early heading date 1 (Ehd1), RICE FLOWERING LOCUS T 1 (RFT1), and Heading date 3a (Hd3a). Functional analysis showed that Ehd5 directly interacts with Rice outermost cell-specific gene 4 (Roc4) and Grain number, plant height, and heading date 8 (Ghd8), which might affect the formation of Ghd7-Ghd8 complexes, resulting in increased expression of Ehd1, Hd3a and RFT1. Taken together, these results demonstrate that Ehd5 functions as a positive regulator of rice flowering and provide insight into the molecular mechanisms underlying heading date.

The Maize ZmBES1/BZR1-9 Transcription Factor Accelerates Flowering in Transgenic Arabidopsis and Rice.

In model plants, the BRI1-EMS suppressor 1 (BES1)/brassinazole-resistant 1 (BZR1) transcription factors play vital roles in regulating growth, development, and stimuli response. However, the roles of maize ZmBES1/BZR1 members are largely unknown. In this research, the ZmBES1/BZR1-9 gene was ectopically expressed in Arabidopsis and rice for the phenotyping of flowering. We found that the complementation and overexpression of ZmBES1/BZR1-9 in bes1-D mutant and wild type Arabidopsis both resulted in early flowering that was about 10 days shorter than in the untransformed control under long-day conditions. In addition, there was no difference in the rosette leaf number between all transgenic lines and the control. Subsequently, the ZmBES1/BZR1-9 gene was overexpressed in rice. It was found that overexpression lines of rice exhibited early flowering with heading dates that were 8 days shorter compared with untransformed plants. Moreover, the results of RNA-seq and qRT-PCR showed that five flowering-regulated genes, namely At2-MMP, AtPCC1, AtMYB56, AtPELPK1, and AtPRP10, were significantly up-regulated in all complementary and overexpressing lines of Arabidopsis. Meanwhile, the results of RNA-seq showed that 69 and 33 differentially expressed genes (DEGs) were up- and down-regulated in transgenic rice, respectively. Four flowering-related genes, namely OsGA20OX1, OsCCR19, OsBTBN19, and OsRNS4 were significantly up-regulated in transgenic lines. To sum up, our findings demonstrate that ZmBES1/BZR1-9 is involved in controlling flowering and provide insights into further underlying roles of BES1/BZR1s in regulating growth and development in crops.

FLOWERING LOCUS T homologue in reblooming bearded iris (Iris spp.) plays a role in accelerating flowering and reblooming

Reblooming bearded iris (Iris spp.) could have two floral initiations and thus two blooming seasons annually. The previous transcriptome profiling has identified a homologue of FLOWERING LOCUS T (FT) as a candidate key gene of reblooming. To further verify its functions in the second floral initiation, the homologue of FT was isolated from the leaves of blooming stems in the flowering stage, named as IgFT, and was functionally characterized. The full-length coding sequence of IgFT was 528bp and encoded 175 amino acids. IgFT in the rebloomers was expressed on a significantly higher level in the second floral initiation stage than that of the first one, but it was scarcely expressed in the floral initiation stage of the once-bloomers, indicating its possible role in reblooming. Moreover, the subcellular location showed that IgFT was mainly located in nucleus. When IgFT was ectopically expressed in Arabidopsis, the five transgenic lines flowered 8.5 d earlier than wild type on average under long-day condition, suggesting it to be a flowering promoter. Moreover, the transgenic lines had more than one basal inflorescences with different flowering date. This phenotype was similar to the reblooming characteristic in bearded iris, namely the in-sequence blooming of different stems from the same rhizome, further supporting the involvement of IgFT in the second floral initiation. Uncovering the functions of IgFT in reblooming could help to investigate the reblooming regulatory network in bearded iris, thereby providing important information for the future molecular breeding of rebloomers.

Genome-Wide Identification, Phylogenetic and Expression Analysis of the B-Box Gene Family in the Woodland Strawberry (Fragaria vesca)

The strawberry (Fragaria × ananassa Duch.) is an important horticultural crop that is widely grown all over the world. Its sweetness, aroma, nutritional value and bright color make it popular. The woodland strawberry (Fragaria vesca) is a model plant for studying non-climacteric fruits because its respiration rate does not change significantly during fruit ripening. The B-box (BBX) protein family is made up of zinc-finger transcription factors important in plant growth and development. In this study, we identified 22 FveBBX genes from the newly released woodland strawberry genome database by comprehensive bioinformatics analysis. Phylogenetic analysis divided these FveBBX genes into five subfamilies. A promoter cis-acting element analysis detected 29 elements related to plant development, light response, abiotic stress and hormone response in the promoter of FveBBX genes. According to transcriptome data, relatively few BBX genes had tissue-specific expression, with examples including FveBBX12, which was expressed only in pre-fertilization cortex and pitch, and FveBBX19, which was specifically expressed in mature anthers. During fruit ripening, the expressions of eight FveBBX genes decreased by more than two-fold, and three FveBBX gene expressions increased more than two-fold both in “Ruegen” and “Yellow Wonder”. After cold and heat stresses, around half of the FveBBX genes displayed altered expression, especially FveBBX16 which showed an 8.3-fold increase in expression after heat treatment, while FveBBX14 showed at least an 11-fold decrease in expression after cold treatment. According to the result of quantitative real-time PCR (qRT-PCR), FveBBX genes’ expression differed depending on the photoperiod. Notably, FveBBX7 gene expression was the opposite during the first 16 h of the long-day (LD) and short-day (SD) conditions. This study provides helpful information for further research on BBX gene activity of the woodland strawberry in plant growth and development and adaptation to temperature and photoperiod environmental conditions.

Expression Analysis and Interaction Protein Screening of CoZTL in Camellia oleifera Abel

Camellia oleifera Abel., which produces fruits of high comprehensive utilization value, is an important woody oil tree in China. ZEITLUPE (ZTL) is a blue light receptor and clock component protein that is involved in various physiological and biochemical processes. However, the expression pattern and function of C. oleifera ZTL (CoZTL) remain unclear. In this study, the coding sequence of the CoZTL gene was isolated and the protein function was explored using bioinformatics and expression analyses and heterologous expression techniques. The results showed that the CoZTL protein was highly conserved during evolution and was on the same branch of the evolutionary tree as the ZTL proteins from Ipomoea nil and Nicotiana attenuata. CoZTL was mainly expressed in the fruit shells and stems of C. oleifera, and its expression level fluctuated greatly during flower bud development. Transgenic CoZTL-overexpressing Arabidopsis plants showed delayed flowering under long-day conditions as well as light-dependent promotion of hypocotyl elongation. Furthermore, yeast two-hybrid library screening revealed that seven C. oleifera proteins (CoAAT, Coβ-GAL, CoLAT52-like, CoCAR4-like, CoAO, CoUQCC1, and CoADF 2) interacted with CoZTL. Our results indicate that CoZTL plays an important role in C. oleifera flowering and hypocotyl growth.

Marker-Assisted Selection for Early Maturing E Loci in Soybean Yielded Prospective Breeding Lines for High Latitudes of Northern Kazakhstan.

The photoperiodic sensitivity of soybean (Glycine max L.) is one of the limiting factors affecting plant growth and yield. At higher latitudes, early flowering and maturity with neutral reaction to photoperiods are required for adaptation of soybean plants to long-day conditions. Currently, the production and distribution of new varieties of soybeans adapted to widespread agricultural regions in northern Kazakhstan is in strong demand. Eleven soybean hybrid populations were obtained from crosses between 17 parents with four maturity groups, MG 000, 00, 0, and I. Marker-assisted selection (MAS) was assessed for suitable SSR markers and successfully applied for genes E1, E3, E4, and E7, targeting homozygous genotypes with recessive alleles. The identified and selected genotypes were propagated and tested in the conditions of 53° N latitude in the Kostanay region of northern Kazakhstan. Finally, 20 early maturing F4 breeding lines were identified and developed with genotypes e1 e3 E4 e7, e1 E3 E4 e7, and e1 E3 e4 e7, all completing their growth period within 92-102 days. These breeding lines were developed by MAS and should provide very prospective superior varieties of soybean for northern Kazakhstan through a strategy that may be very helpful to other countries with high latitudes.

Response of the organellar and nuclear (post)transcriptomes of Arabidopsis to drought.

Plants have evolved sophisticated mechanisms to cope with drought, which involve massive changes in nuclear gene expression. However, little is known about the roles of post-transcriptional processing of nuclear or organellar transcripts and how meaningful these changes are. To address these issues, we used RNA-sequencing after ribosomal RNA depletion to monitor (post)transcriptional changes during different times of drought exposure in Arabidopsis Col-0. Concerning the changes detected in the organellar transcriptomes, chloroplast transcript levels were globally reduced, editing efficiency dropped, but splicing was not affected. Mitochondrial transcripts were slightly elevated, while editing and splicing were unchanged. Conversely, alternative splicing (AS) affected nearly 1,500 genes (9% of expressed nuclear genes). Of these, 42% were regulated solely at the level of AS, representing transcripts that would have gone unnoticed in a microarray-based approach. Moreover, we identified 927 isoform switching events. We provide a table of the most interesting candidates, and as proof of principle, increased drought tolerance of the carbonic anhydrase ca1 and ca2 mutants is shown. In addition, altering the relative contributions of the spliced isoforms could increase drought resistance. For example, our data suggest that the accumulation of a nonfunctional FLM (FLOWERING LOCUS M) isoform and not the ratio of FLM-ß and -δ isoforms may be responsible for the phenotype of early flowering under long-day drought conditions. In sum, our data show that AS enhances proteome diversity to counteract drought stress and represent a valuable resource that will facilitate the development of new strategies to improve plant performance under drought.

Unique morphology and photoperiodically regulated activity of neurosecretory canopy cells in the pond snail Lymnaea stagnalis

The pond snail Lymnaea stagnalis exhibits clear photoperiodism in egg laying; it lays more eggs in long-day conditions than in medium-day conditions. A key regulator of egg laying is neurosecretory caudo-dorsal cells (CDCs) producing an ovulation hormone in the cerebral ganglia. Paired small budding structures of the cerebral ganglia (viz. the lateral lobe) also promote egg laying in addition to spermatogenesis and maturation of female accessory sex organs. However, it remains unknown which cells in the lateral lobe are responsible for these. Previous anatomical and physiological studies prompted us to hypothesize that canopy cells in the lateral lobe modulate activity of CDCs. However, double labeling of the canopy cell and CDCs revealed no sign of direct neural connections, suggesting that activity of CDCs is regulated either humorally or through a neural pathway independent of canopy cells. In addition, our detailed anatomical re-evaluation confirmed previous observations that the canopy cell bears fine neurites along the ipsilateral axon and extensions from the plasma membrane of the cell body, although the function of these extensions remains unexplored. Furthermore, comparison of electrophysiological properties between long-day and medium-day conditions indicated that the canopy cell’s activity is moderately under photoperiodic regulation: resting membrane potentials of long-day snails are shallower than those of medium-day snails, and spontaneously spiking neurons are only observed in long-day conditions. Thus, canopy cells appear to receive photoperiodic information and regulate photoperiod-dependent phenomena, but not provide direct neural inputs to CDCs.

The transcription factor HBF1 directly activates expression of multiple flowering time repressors to delay rice flowering.

The online version contains supplementary material available at 10.1007/s42994-023-00107-7.

CONSTANS interacts with and antagonizes ABF transcription factors during salt stress under long-day conditions.

CONSTANS (CO) is a critical regulator of flowering that combines photoperiodic and circadian signals in Arabidopsis (Arabidopsis thaliana). CO is expressed in multiple tissues, including seedling roots and young leaves. However, the roles and underlying mechanisms of CO in modulating physiological processes outside of flowering remain obscure. Here, we show that the expression of CO responds to salinity treatment. CO negatively mediated salinity tolerance under long-day (LD) conditions. Seedlings from co-mutants were more tolerant to salinity stress, whereas overexpression of CO resulted in plants with reduced tolerance to salinity stress. Further genetic analyses revealed the negative involvement of GIGANTEA (GI) in salinity tolerance requires a functional CO. Mechanistic analysis demonstrated that CO physically interacts with 4 critical basic leucine zipper (bZIP) transcription factors; ABSCISIC ACID-RESPONSIVE ELEMENT BINDING FACTOR1 (ABF1), ABF2, ABF3, and ABF4. Disrupting these ABFs made plants hypersensitive to salinity stress, demonstrating that ABFs enhance salinity tolerance. Moreover, ABF mutations largely rescued the salinity-tolerant phenotype of co-mutants. CO suppresses the expression of several salinity-responsive genes and influences the transcriptional regulation function of ABF3. Collectively, our results show that the LD-induced CO works antagonistically with ABFs to modulate salinity responses, thus revealing how CO negatively regulates plant adaptation to salinity stress.

Influence of genotype and bacterization on growth, development, and soluble carbohydrate content in soybean E-genes isogenic lines

Photoperiod, which regulates the duration of vegetative and generative development, and the plant-microorganism interaction, which influences the metabolic status of plant organisms, are important factors in the regulating plant growth and development. The aim of the study was to determine the influence of Glycine max (L.) Merr. genotype and seed pre-bacterization with a virulent and active strain of Bradyrhizobium japonicum 634b on the plant growth and development, and on the soluble carbohydrate content in leaves of isogenic by E-genes lines under field conditions. Nearly isogenic lines (NILs) of soybean, in which the E1, E2, and E3 genes are located at different allelic loci, were used. Sterile seeds were pretreated with distilled water (control) and Bradyrhizobium japonicum 634b cell suspension (experiment). Plants were grown under natural long-day conditions (16 hours). The growth and development of the soybean were evaluated by phenological observations, morphometric indicators fixed at the V3 and V5 developmental stages, relative growth rate (RGR), and the content of soluble sugars ‒ mono- and oligosaccharides. The effect of the factors studied (genotype, bacterization, and their interaction) was calculated. The results of the experiment and the calculation of the effect of the factor showed that the isoline genotype has the greatest effect on seed germination, phenological development of the plant and duration of the VE-R1 phase, growth of the root system in the V3 and V5 phases, and the content of monosaccharides involved in forming the plant-microorganism interaction. The effect of bacterization is most evident in the RGR, shoot development, and the oligosaccharide content of the leaves of NILs in the V3 and V5 phases. Among the isolines studied, L 80-5879, which has the E1 gene (flowering repressor) in a dominant state, was characterized by minimal sensitivity to bacterization. It was found that bacterization and genotype interaction didn't influence the VE-R1 duration stage and the shoot and root length. The results obtained therefore prove that the E-series genes, which determine the photoperiodic sensitivity of soya beans, can also be indirectly involved in establishing plant-microorganism interactions.

Photoperiod and gravistimulation-associated Tiller Angle Control 1 modulates dynamic changes in rice plant architecture.

TAC1 is involved in photoperiodic and gravitropic responses to modulate rice dynamic plant architecture likely by affecting endogenous auxin distribution, which could explain TAC1 widespread distribution in indica rice. Plants experience a changing environment throughout their growth, which requires dynamic adjustments of plant architecture in response to these environmental cues. Our previous study demonstrated that Tiller Angle Control 1 (TAC1) modulates dynamic changes in plant architecture in rice; however, the underlying regulatory mechanisms remain largely unknown. In this study, we show that TAC1 regulates plant architecture in an expression dose-dependent manner, is highly expressed in stems, and exhibits dynamic expression in tiller bases during the growth period. Photoperiodic treatments revealed that TAC1 expression shows circadian rhythm and is more abundant during the dark period than during the light period and under short-day conditions than under long-day conditions. Therefore, it contributes to dynamic plant architecture under long-day conditions and loose plant architecture under short-day conditions. Gravity treatments showed that TAC1 is induced by gravistimulation and negatively regulates shoot gravitropism, likely by affecting auxin distribution. Notably, the tested indica rice containing TAC1 displayed dynamic plant architecture under natural long-day conditions, likely explaining the widespread distribution of TAC1 in indica rice. Our results provide new insights into TAC1-mediated regulatory mechanisms for dynamic changes in rice plant architecture.

A novel MORN-motif type gene GmMRF2 controls flowering time and plant height of soybean

The flowering time of soybean is a highly important agronomic characteristic, which affects the adaptability and yield. AtMRF1, a MORN-repeat motif gene, acts as a floral promoter in Arabidopsis, its functions in soybean are not yet understood. Here, we employed qRT-PCR to analyze the tissue expression patten of MRF1 homologs in soybean and determined that the GmMRF2 gene, containing a MORN-motif, highly expressed in the shoot and responded to photoperiod. GmMRF2 overexpression soybean lines exhibited earlier flowering time under long-day (LD) conditions, and increased plant height under both LD and short-day (SD) conditions compared to wild-type (WT) plants. The expression levels of gibberellic acid (GA) pathway genes that positively regulate plant height genes and flowering-promoting genes were up-regulated in the GmMRF2 overexpression lines, were up-regulated in the GmMRF2 overexpression lines. Further study revealed that GmMRF2 interacted with GmTCP15 to co-induce the expression of GmSOC1b. Together, our results preliminarily reveal the functions and mechanisms of GmMRF2 in regulating flowering time and plant height, provide a new promising gene for soybean crop improvement.

Blocking the Expression of the Nitrate Reductase Gene OsNia3 Confers Early Maturation in Rice

Early flowering is a major contributing factor to early crop maturation and is a prerequisite for the expansion of crop production to high latitudes with short growing seasons as well as for annual double/triple cropping systems. Nitrogen is the mineral element most limiting to plant growth and, consequently, also to crop yield. Nitrogen also plays a role in the regulation of flowering time. Here, we show that OsNia3 is a member of the rice nitrate reductase (NR) gene family. OsNia3 was found to be expressed in stem nodes of rice, while the loss of its function led to a reduction in plant height mainly due to disrupted nitrate metabolism at the site of OsNia3 expression. The expression levels of genes related to nitrate transport, nitrate assimilation, and ammonium assimilation, such as OsNia1, OsNRT2.3A, and OsNGS1, increased in the leaves of osnia3 mutant plants, concomitant with an increase in the activity of the nitrogen metabolism pathway. The ammonium and amino acid contents in the leaves also increased in the osnia3 mutant, as did the chlorophyll content. Phenotypic analysis showed that the osnia3 mutant exhibited a shorter growth period compared with wild-type plants; nevertheless, yield was not significantly affected in mutant plants. The deletion of the OsNia3 gene led to the upregulation of genes related to the photoperiod regulation network (OsGI, OsHd1, and OsHd3a), which likely promoted early flowering. These results indicated that OsNia3 is involved in the floral inhibition pathway (OsGI-OsHd1-OsHd3a) in rice under long-day conditions. Our findings provide a theoretical and material basis for the coordination and improvement of early maturity and high-yield traits in rice breeding.

Очень ранний сорт сои Забава

A very early soybean variety Zabava was selected from the hybrid combination F4 Slavia × EU Mentor by traits of increased cold resistance, drought resistance and reduced reaction for the length of the day. The Zabava variety belongs to a very early group of maturity, at the latitude of Krasnodar (45°) it matures in 94 days, and in yield is not inferior to the Puma standard variety. At the latitude of Samara (53°), it matures in 95 days, and the yield significantly exceeds the Samer 3 standard variety. In 2022, in a competitive variety test in the Krasnodar region, its yield was 2.51 t/ha; in a competitive test in the Samara region, it was 3.33 t/ha. The height of the plants of the Zabava variety at the latitude of Krasnodar averaged 74 cm. In the Samara region, at latitude 53°, the height of plants of the Zabava variety increased slightly to 87 cm. High resistance to low air and soil temperatures in the germination phase, and increased yield in long-day conditions characterizes the new soybean variety Zabava. This allows it to be cultivated in soybean-producing farms in the Central Chernozem, North Caucasus, Middle Volga, Low Volga, Ural, Western Siberian and Eastern Siberian regions of the Russian Federation.

Effects of the quantitative trait locus qPss3 on inhibition of photoperiod sensitivity and resistance to stalk rot disease in maize.

We identified a quantitative trait locus, qPss3, and fine-mapped the causal locus to a 120-kb interval in maize. This locus inhibits the photoperiod sensitivity caused by ZmCCT9 and ZmCCT10, resulting in earlier flowering by 2 ~ 4days without reduction in stalk-rot resistance in certain genotypes. Photoperiod sensitivity is a key factor affecting the adaptation of maize (Zea mays L.) to high-latitude growing areas. Although many genes associated with flowering time have been identified in maize, no gene that inhibits photoperiod sensitivity has been reported. In our previous study, we detected large differences in photoperiod sensitivity among maize inbred lines with the same photoperiod-sensitive allele at the ZmCCT10 locus. Here, we used two segregating populations with the same genetic backgrounds but different ZmCCT10 alleles to perform quantitative trait locus (QTL) analysis. We identified a unique QTL, qPss3, on chromosome 3 in the population carrying the sensitive ZmCCT10 allele. After sequential fine-mapping, we eventually delimited qPss3 to an interval of ~ 120kb. qPss3 behaved as a dominant locus and caused earlier flowering by 2-4days via inhibiting ZmCCT10-induced photoperiod sensitivity under long-day conditions. qPss3 also inhibited the photoperiod sensitivity induced by another flowering-related gene, ZmCCT9. For application in agriculture, an F1 hybrid heterozygous at both qPss3 and ZmCCT10 loci constitutes an optimal allele combination, showing high resistance to stalk rot without a significant delay in flowering time. Moreover, qPss3 is of great value in regulating the flowering time of tropical maize grown at high-latitude regions.

Temperature compensation and entrainment in cyanobacteria circadian rhythm

ABSTRACT Circadian rhythm is an endogenous rhythmic behavior of organisms used to adapt to the external environment. Although most biochemical reactions accelerate with increasing temperature, the period of circadian rhythms remains relatively stable across a range of temperature, a phenomenon known as temperature compensation. Meanwhile, circadian rhythms can be reset by environmental signals, such as daily periodic light or temperature, a phenomenon known as entrainment. Cyanobacteria are the simplest organisms to have circadian rhythms. The effect of light on cyanobacteria circadian rhythm has been widely studied with mathematical models. However, the effect of temperature on cyanobacteria circadian rhythm and the mechanisms of temperature compensation and entrainment are far from clear. In this paper, we apply a recent model to incorporate temperature dependence by Van’t Hoff rule. With numerical simulation, we study the temperature compensation and entrainment in detail. The results show that the system can exhibit temperature compensation when the post-transcription process is insensitive to temperature. The temperature compensation is caused by the cancellation of the increase of amplitude and the acceleration of speed, resulting in the stable period, when the temperature rises. The system can also exhibit temperature entrainment in constant light in a very limited temperature range. When the periodic light is added simultaneously to simulate more realistic environment, the temperature range of entrainment is greatly improved. The results also suggest that long-day condition is conducive to entrainment. The findings of this paper provide a theoretical reference for biological research and help us understand the dynamical mechanisms of cyanobacteria circadian rhythm.