Short-day Treatment Research Articles

Flowering response of diverse chickpea (Cicer arietinum L.) accessions to photoperiod

Knowledge of the time required for the initiation of flowering is important for chickpea adaptation in environments like western Canada, not only because flowering is a vulnerable stage of development but also it is a major factor affecting variation in crop duration. Temperature and photoperiod are the major environmental factors that determine time to flowering in many major crops. One hundred diverse chickpea accessions were examined under long-day (16/8 H day and night, respectively) and short day (10/14 H day and night, respectively) photoperiods for their flowering response. The temperature in the chambers was adjusted to 22/16 °C (day and night, respectively). Variability among the accessions for days to flowering, photoperiod sensitivity (defined as the delayed number of days to flowering under short-day photoperiod treatment as compared to long-day photoperiod treatments), and node number of first flowering under short and long-day photoperiods was detected. Four accessions were classified as photoperiod-insensitive, 49 as intermediate response, and 47 as highly photoperiod-sensitive based on their flowering response to photoperiod. A significant (r = 0.92, P ≤ 0.0001) positive correlation was observed between days to flowering under short-days and photoperiod sensitivity. In photoperiod-insensitive accessions fewer degree days were required for flowering as compared to intermediate and highly photoperiod sensitive ones. Under long-day photoperiod, the photo-thermal and thermal units required to initiate flowering accumulate faster. Thus photoperiod-insensitive accessions required fewer accumulated thermal and photo-thermal units.

Morphogenesis, Flowering, and Gene Expression of Dendranthema grandiflorum in Response to Shift in Light Quality of Night Interruption.

The impact of shifts in the spectral quality of light on morphogenesis, flowering, and photoperiodic gene expression during exposure to light quality of night interruption (NI) was investigated in Dendranthema grandiflorum. The circadian rhythms of plants grown in a closed walk-in growth chamber were interrupted at night for a total of 4 h, using light-emitting diodes with an intensity of 10 μmol·m−2·s−1 PPF. The light quality of the NI was shifted from one wavelength to another after the first 2 h. Light treatments consisting of all possible pairings of blue (B), red (R), far-red (Fr), and white (W) light were tested. Plants in the NI treatment groups exposed to Fr light grew larger than plants in other treatment groups. Of plants in NI treatment groups, those in the NI-WB treatment grew the least. In addition, the impact of shifts in the light quality of NI on leaf expansion was greater in treatment groups exposed to a combination of either B and R or R and W light, regardless of their order of supply. Flowering was observed in the NI-RB, NI-FrR, NI-BFr, NI-FrB, NI-WB, NI-FrW, NI-WFr, NI-WR, and SD (short-day) treatments, and was especially promoted in the NI-BFr and NI-FrB treatments. In a combined shift treatment of B and R or B and W light, the NI concluded with B light (NI-RB and NI-WB) treatment induced flowering. The transcriptional factors phyA, cry1 and FTL (FLOWERING LOCUS T) were positively affected, while phyB and AFT were negatively affected. In conclusion, morphogenesis, flowering, and transcriptional factors were all significantly affected either positively or negatively by shifts in the light quality of NI. The light quality of the first 2 h of NI affected neither morphogenesis nor flowering, while the light quality of the last 2 h of NI significantly affected both morphogenesis and flowering.

Identification of MicroRNAs in Response to Different Day Lengths in Soybean Using High-Throughput Sequencing and qRT-PCR.

MicroRNAs (miRNAs) are short, non-coding single-strand RNA molecules that play important roles in plant growth, development and stress responses. Flowering time affects the seed yield and quality of soybean. However, the miRNAs involved in the regulation of flowering time in soybean have not been reported until recently. Here, high-throughput sequencing and qRT-PCR were used to identify miRNAs involved in soybean photoperiodic pathways. The first trifoliate leaves of soybean that receive the signal of light treatment were used to construct six libraries (0, 8, and 16 h under short-day (SD) treatment and 0, 8, and 16 h under long-day (LD) treatment). The libraries were sequenced using Illumina Solexa. A total of 318 known plant miRNAs belonging to 163 miRNA families and 81 novel predicted miRNAs were identified. Among these, 23 miRNAs at 0 h, 65 miRNAs at 8 h and 83 miRNAs at 16 h, including six novel predicted miRNAs at 8 h and six novel predicted miRNAs at 16 h, showed differences in abundance between LD and SD treatments. Furthermore, the results of GO and KEGG analyses indicated that most of the miRNA targets were transcription factors. Seven miRNAs at 0 h, 23 miRNAs (including four novel predicted miRNAs) at 8 h, 16 miRNAs (including one novel predicted miRNA) at 16 h and miRNA targets were selected for qRT-PCR analysis to assess the accuracy of the sequencing and target prediction. The results indicated that the expression patterns of the selected miRNAs and miRNA targets showed no differences between the qRT-PCR and sequencing results. In addition, 23 miRNAs at 0 h, 65 miRNAs at 8 h and 83 miRNAs at 16 h responded to day length changes in soybean, including six novel predicted miRNAs at 8 h and six novel predicted miRNAs at 16 h. These results provided an important molecular basis to understand the regulation of flowering time through photoperiodic pathways in soybean.

The effect of photoperiod on life history and blood-feeding activity in Aedes albopictus and Aedes aegypti (Diptera: Culicidae).

Several studies have examined how climatic variables such as temperature and precipitation may affect life history traits in mosquitoes that are important to disease transmission. Despite its importance as a seasonal cue in nature, studies investigating the influence of photoperiod on such traits are relatively few. This study aims to investigate how photoperiod alters life history traits, survival, and blood-feeding activity in Aedes albopictus (Skuse) and Aedes aegypti (Linnaeus). We performed three experiments that tested the effects of day length on female survival, development time, adult size, fecundity, adult life span, and propensity to blood feed in Ae. albopictus and Ae. aegypti. Each experiment had three photoperiod treatments: 1) short-day (10L:14D), 2) control (12L:12D), and 3) long-day (14L:10D). Aedes albopictus adult females were consistently larger in size when reared in short-day conditions. Aedes aegypti adult females from short-day treatments lived longer and were more likely to take a blood meal compared to other treatments. We discuss how species-specific responses may reflect alternative strategies evolved to increase survival during unfavorable conditions. We review the potential impacts of these responses on seasonal transmission patterns, such as potentially increasing vectorial capacity of Ae. aegypti during periods of shorter day lengths.

Growing rice in controlled environments

Rice (Oryza sativa) is less frequently used in basic research than Arabidopsis, although rice is a valuable model system for many monocot crops and possesses a high genetic variability in physiologically as well as agriculturally relevant features such as abiotic stress tolerance, nutrient efficiency and flower time control. A reason is the seemingly difficult cultivation of rice outside the rice production area. This review aims to assist newcomers to the field to develop cultivation protocols for their local controlled environment. The main challenges are high light demands, photoperiodicity and low micronutrient efficiency. The nutrient efficiency problem can be overcome by adding micronutrient fertiliser to potting substrates and keeping the soil waterlogged to increase micronutrient availability and mobility. Cultivation of rice on adjusted hydroponic solutions with high iron concentration provides the basis for successful heavy isotope labelling. Many rice cultivars need high light intensities in combination with short-day conditions to complete their life cycle. However, some photoperiod-insensitive cultivars will flower even under relatively low light intensities. In highly photoperiod-sensitive cultivars, like Nipponbare, flowering can be induced by a limited period of short-day treatment in the sensitive period, after which the cultivation can be continued in long-day conditions. The life cycle of many cultivars is completed in 90 to 120 days, its length being thus comparable to Arabidopsis and shorter than in other cereals. In conclusion, with the right cultivation technique, rice is an amiable model species for researchers beyond the rice area too.

Constitutive expression of the Poplar FD-like basic leucine zipper transcription factor alters growth and bud development.

In poplar, the CO/FT regulatory module mediates seasonal growth cessation. Although FT interacts with the basic leucine zipper transcription factor FD, surprisingly little is known about the possible role of FD in bud development and growth cessation in trees. In this study, we examined the expression and localization of the poplar FD homolog, PtFD1, during short-day (SD)-induced bud development, and the consequences of overexpressing PtFD1 on bud development and shoot growth. PtFD1 was primarily expressed in apical and axillary buds and exhibited a transient increase in expression during the initial stages of SD-induced bud development. This transient increase declined with continued SD treatment. When PtFD1 was overexpressed in poplar, SD-induced growth cessation and bud formation were abolished. PTFD1 overexpression also resulted in precocious flowering of juvenile plants in long-day (LD) photoperiods. Because the phenotypes associated with overexpression of PtFD1 are similar to those observe when poplar FT1 is overexpressed (Science, 312, 2006, 1040), the expression and diurnal patterns of expression of both poplar FT1 and FT2 were characterized in PtFD1 overexpression poplars and found to be altered. DNA microarray analysis revealed few differences in gene expression between PtFD1 overexpressing poplars in LD conditions while extensive levels of differential gene expression occur in SD-treated plants. These results enforce the connection between the regulation of flowering and the regulation of growth cessation and bud development in poplar.

Photosynthetic activities, C<sub>3</sub> and C<sub>4</sub> indicative enzymes and the role of photoperiod in dormancy induction in 'Chunjie' peach

Our study examined the relationship between photosynthetic performance and activities of key photosynthetic enzymes to understand the photosynthetic variation and reasons for the variation during dormancy induction under different photoperiods in peach (Prunus persica L. cv. Chunjie). Furthermore, the study explained the changes in the key enzymes from the viewpoint of differential proteomics. The results showed that the leaf net photosynthetic rate (PN) and stomatal conductance tended to decrease, while the intercellular CO2 concentration rose, which indicated that the reduced PN resulted from nonstomatal limitation. During the dormancy induction period, the activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC) declined, which was the main reason for the reduced PN. Two-dimensional electrophoresis maps and differential protein identification demonstrated that the decrease in activity of the photosynthetic enzymes was mainly due to enzymatic degradation. The enzyme degradation by a long-day treatment occurred later and to a lesser degree than that of the short-day treatment. In the long-day treatment, the carboxylation activity of Rubisco was higher than that of the control treatment, and the PEPC activity and the ratio of the PEPC/Rubisco activity were lower than the corresponding activities during the control treatment. These differences under long-day conditions were significant but did not occur in the short-day treatment, suggesting that the C4 pathway might be more active under short-day conditions.

Photoperiod and shading regulate coloration and anthocyanin accumulation in the leaves of malus crabapples

In many ornamental plants, anthocyanin accumulation in leaves is a critical determinant of foliage coloration. However, the mechanism by which photoperiod and shading affect coloration and anthocyanin accumulation in the leaves of woody plants is less clear. By examining the leaves and calli of crabapple (Malus spp.) cultivars with different leaf color characteristics, we analyzed the foliage coloration, flavonoid contents, and expression levels of anthocyanin biosynthetic genes and the McMYB10 transcription factor under different photoperiods and shading treatments. The red color parameters, flavonoid contents, and expression levels of some anthocyanin-related genes in both the leaf and callus were generally higher under sun-exposure or long-day treatments compared to shading or short-day treatments. These data indicate that red color formation in cultivars with leaves that are naturally red requires a suitable photoperiod and light intensity; high light intensity or long-day conditions activate anthocyanin biosynthesis-related genes, leading to anthocyanin accumulation. Our results also indicate that the regulation of anthocyanin biosynthetic metabolism in response to light conditions differs between red-leafed and green-leafed cultivars. Taken together, our data reveal that photoperiod and light intensity are important in the regulation of pigmentation and anthocyanin accumulation in crabapple leaves and calli. Moreover, we provide a useful approach for studying and inducing the production of flavonoids by crabapple callus culture under certain photoperiods.

Post-planting effects of early-season short-day treatment and summer planting on Norway spruce seedlings

Effects of short-day (SD) treatment on bud burst, growth and survival of Norway spruce ( [L.] Karst.) container seedlings after summer planting were studied in an experiment established in Suonenjoki, Central Finland. One-year-old seedlings were SD-treated for three weeks starting on 18 June, 24 June and 8 July 2004 and then planted on 22 July, 5 August, 6 September 2004 and, as a normal spring planting, on 10 May, 2005. Untreated control seedlings were also planted on these dates. Second flush on the planting year and bud burst the following spring was monitored in planted seedlings, whereas seedling height and survival were determined at the end of growing seasons 2004–2006. We observed a non-significant risk of a second flush if seedlings were SD-treated on 18 June. Also, SD-treated seedlings planted in July or August showed advanced bud burst and increased height the following growing season without significant effects on survival, compared to autumn and spring planted seedlings. Planting in July or early August was associated with a significant increase in the incidence of multiple leaders in later years. Based on our results, to begin a three-week SD treatment in late June or early July and then plant seedlings in late July or early August could be a good practice.Picea abies

Controlling Flowering of Photoperiodic Ornamental Crops with Light-emitting Diode Lamps: A Coordinated Grower Trial

Photoperiodic lighting from lamps with a moderate ratio of red [R (600–700 nm)] to far-red [FR (700–800 nm)] light effectively promotes flowering of long-day plants (LDPs). Because of spectral controllability, long life span, and energy efficiency, light-emitting diodes (LEDs) have emerged as an alternative to conventional light sources, such as incandescent (INC) and high-pressure sodium (HPS) lamps. We conducted a coordinated trial with five commercial greenhouse growers to investigate the efficacy of R + white (W) + FR LEDs, with an R:FR of 0.82, to regulate flowering of daylength-sensitive ornamental crops. The trial was also performed in two replicate greenhouses at Michigan State University (MSU). Ageratum (Ageratum houstonianum), calibrachoa (Calibrachoa ×hybrida), dahlia (Dahlia ×hybrida), dianthus (Dianthus chinensis), petunia (Petunia ×hybrida), snapdragon (Antirrhinum majus), and verbena (Verbena ×hybrida) were grown under natural short days (SDs) with 4-hour night-interruption (NI) lighting provided by the R + W + FR LEDs or conventional lamps typically used by each grower. Two companies used HPS lamps, whereas the other sites used INC lamps. In addition, a natural SD treatment, a truncated 9-hour SD treatment, or a compact fluorescent lamp (CFL) NI treatment was provided at three different sites. With few exceptions, time to flower and flowering percentage of the bedding plant crops tested were similar under the R + W + FR LEDs to that under the conventional lamps at all sites. At MSU, ageratum, dianthus, petunia, snapdragon, and verbena flowered earlier under NI lighting treatments than under 9-hour SDs. In addition, plant height and visible flower bud or inflorescence number at flowering were similar under the R + W + FR LEDs and INC lamps for most crops. Therefore, we conclude that the R + W + FR LEDs are as effective as lamps traditionally used in greenhouses at controlling flowering of photoperiodic plants.

Optimal temperature and light conditions for germination of Elymus glabriflorus

As of date, information regarding seed physiology and germination requirements of southeastern wildrye ( Elymus glabriflorus (Vasey ex L.H. Dewey) Scribn. & C.R. Ball [Poaceae]) is limited. Five seed accessions were collected across a variety of habitats at different latitudes and were placed under a range of temperature and light regimes to determine optimal conditions for germination. Temperature treatments for germination included alternating day/night regimes from 10 to 25 °C in 5° increments. Light testing consisted of 4 treatments: constant light, constant dark, short day (8 h), and long day (16 h). Results from the temperature experiment indicated no correlation between latitude and temperature for optimal germination. The collection from the southernmost site, Laurel, Mississippi, and the northernmost site, Upton, Kentucky, had an optimal germination temperature of 20 °C. The short-day (8-h) treatment had the greatest initial germination (41% for 2010 and 61% for 2013). These results indicate that temperature requirements for germination of E. glabriflorus seed range from 15 to 20 °C and that shortening day length (

Light quality regulates flowering in FvFT1/FvTFL1 dependent manner in the woodland strawberry Fragaria vesca.

Control of flowering in the perennial model, the woodland strawberry (Fragaria vesca L.), involves distinct molecular mechanisms that result in contrasting photoperiodic flowering responses and growth cycles in different accessions. The F. vesca homolog of TERMINAL FLOWER1 (FvTFL1) functions as a key floral repressor that causes short-day (SD) requirement of flowering and seasonal flowering habit in the SD strawberry. In contrast, perpetual flowering F. vesca accessions lacking functional FvTFL1 show FLOWERING LOCUS T (FvFT1)-dependent early flowering specifically under long-days (LD). We show here that the end-of-day far-red (FR) and blue (B) light activate the expression of FvFT1 and the F. vesca homolog of SUPPRESSOR OF THE OVEREXPRESSION OF CONSTANS (FvSOC1) in both SD and LD strawberries, whereas low expression levels are detected in red (R) and SD treatments. By using transgenic lines, we demonstrate that FvFT1 advances flowering under FR and B treatments compared to R and SD treatments in the LD strawberry, and that FvSOC1 is specifically needed for the B light response. In the SD strawberry, flowering responses to these light quality treatments are reversed due to up-regulation of the floral repressor FvTFL1 in parallel with FvFT1 and FvSOC1. Our data highlights the central role of FvFT1 in the light quality dependent flower induction in the LD strawberry and demonstrates that FvTFL1 reverses not only photoperiodic requirements but also light quality effects on flower induction in the SD strawberry.

Stress enhances the gene expression and enzyme activity of phenylalanine ammonia-lyase and the endogenous content of salicylic acid to induce flowering in pharbitis

The involvement of salicylic acid (SA) in the regulation of stress-induced flowering in the short-day plant pharbitis (also called Japanese morning glory) Ipomoea nil (formerly Pharbitis nil) was studied. Pharbitis cv. Violet was induced to flower when grown in 1/100-strength mineral nutrient solution under non-inductive long-day conditions. All fully expanded true leaves were removed from seedlings, leaving only the cotyledons, and flowering was induced under poor-nutrition stress conditions. This indicates that cotyledons can play a role in the regulation of poor-nutrition stress-induced flowering. The expression of the pharbitis homolog of PHENYLALANINE AMMONIA-LYASE, the enzyme activity of phenylalanine ammonia-lyase (PAL; E.C. 4.3.1.5) and the content of SA in the cotyledons were all up-regulated by the stress treatment. The Violet was also induced to flower by low-temperature stress, DNA demethylation and short-day treatment. Low-temperature stress enhanced PAL activity, whereas non-stress factors such as DNA demethylation and short-day treatment decreased the activity. The PAL enzyme activity was also examined in another cultivar, Tendan, obtaining similar results to Violet. The exogenously applied SA did not induce flowering under non-stress conditions but did promote flowering under weak stress conditions in both cultivars. These results suggest that stress-induced flowering in pharbitis is induced, at least partly, by SA, and the synthesis of SA is promoted by PAL.

Photoperiodic variations induce shifts in the leaf metabolic profile of Chrysanthemum morifolium.

Plants have a high ability to adjust their metabolism, growth and development to changes in the light environment and to photoperiodic variation, but the current knowledge on how changes in metabolite contents are associated with growth and development is limited. We investigated the effect of three different photoperiodic treatments with similar daily light integral (DLI) on the growth responses and diurnal patterns in detected leaf metabolites in the short day plant Chrysanthemum×morifolium Ramat. Treatments were long day (LD, 18h light/6h dark), short day (SD, 12h light/12h dark) and short day with irregular night interruptions (NI-SD,12h light/12h dark, applied in a weekly pattern, shifting from day-to-day). Photoperiodic variation resulted in changes in the phenotypic development of the plants. The plants grown in the SD treatment started to initiate reproductive development of the meristems and a decrease in leaf expansion resulted in lower leaf area of expanding leaves. In contrast, plants in the NI-SD and LD treatments did not show reproductive development at any stage and final leaf area of the expanding leaves was intermediate for the NI-SD plants and largest for the LD plants. Photoperiodic variation also resulted in changes in the leaf metabolic profile for most of the analysed metabolites, but only carbohydrates, citrate and some amino acids displayed a shift in their diurnal pattern. Further, our results illustrated that short days (SD) increased the diurnal turnover of 1-kestose after 2 weeks, and decreased the overall contents of leaf hexoses after 3 weeks. In the two other treatments a diurnal turnover of 1-kestose was not stimulated before after 3 weeks, and hexoses together with the hexose:sucrose ratio steadily increased during the experiment. Our results enlighten the plasticity of leaf growth and metabolism to environmental changes, and demonstrate that diurnally regulated metabolites not always respond to photoperiodic variation.

적색 LED(660nm)의 광중단 처리에 따른 국화 '백마'와 '신마'의 화아분화 및 생육특성

This study was carried out to examine the effect of Red LED (660 nm) and fluorescent lamp for night break (NB) treatments of each 3 hours (22:30-01:30), 4 hours (22:00-02:00) and 5 hours (21:30-:02:30) per day for 53 days on flower bud initiation and growth in Chrysanthemum cv. 'Baekma' and cv. 'Jinba'. The days to flower budding after short-day treatment in 'Baekma' was longer at fluorescent lamp 4 hr (21.0 days) and 5 hr (20.5 days) NB, and it was shorter at Red LED 3 hr (14.2 days). The days to flowering after short-day treatment in 'Baekma' was longer at fluorescent lamp 4 hr (54.0 days), 5 hr (53.5 days) NB, and Red LED 5 hr (53.3 days), and it was shortest at Red LED 3 hr (50.2 days) NB treatment among all treatments. The days to flower budding after short-day treatment of 'Jinba' was longer at fluorescent lamp 4 hr (20.6 days) and was shorter at Red LED 3 hr (14.1 days) among all treatments. Similarly, the days to flowering after short-day treatment of 'Jinba' was longer at fluorescent lamp 4 hr (55.3 days) and was shortest at Red LED 3 hr (50.2 days) among all treatments. Therefore, inhibition of flower bud initiation was the most effective under fluorescent lamp 4 hr treatment. The length of cut flower of 'Baekma' was increased by fluorescent lamp 4 hr, 5 hr, and Red LED 5 hr, but of 'Jinba' was longer at LED 4 hr and 5 hr treatment. The weight of cut flower of 'Baekma' was heaviest at fluorescent lamp 5 hr treatment and was at Red LED 5hr treatment for 'Jinba' even though there was not statistically significant difference between 'Baekma' and 'Jinba'. Consequently, under fluorescent lamp 4 hr for night break was the most effective on flower bud initiation, flowering inhibition and cut-flower characteristics in 'Baekma' and 'Jinba'.

Characterization of Chrysanthemum ClSOC1-1 and ClSOC1-2, homologous genes of SOC1

The MADS-box gene SOC1/TM3 (SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1/ Tomato MADS-box gene 3) is a main integrator in the Arabidopsis flowering pathway; its structure and function are highly conserved in many plant species. SOC1-like genes have been isolated in chrysanthemum, one of the most well-known ornamental plants, but it has not been well characterized thus far. We isolated and characterized ClSOC1-1 and ClSOC1-2, two putative orthologs of Arabidopsis SOC1, from the wild diploid chrysanthemum, Chrysanthemum lavandulifolium, to investigate the regulatory mechanisms of flowering time control in chrysanthemum. Expression analysis indicated that ClSOC1-1 and ClSOC1-2 were expressed in all examined organs/tissues (leaves, shoot apices, petioles, stems and roots) with different expression levels, and with high expression in the shoot apices and leaves during the early stage of floral transition. The expression levels of ClSOC1-1 and ClSOC1-2 in the shoot apices increased at different developmental stages with the highest expression levels after 7 days of short-day treatment. Overexpression of ClSOC1-1 and ClSOC1-2 in wild-type Arabidopsis resulted in early flowering, which was coupled with the upregulation of one of the flowering promoter genes LEAFY. Our results suggested that the ClSOC1-1 and ClSOC1-2 genes play an evolutionarily conserved role in promoting flowering in Chrysanthemum lavandulifolium and could serve as a vital target for the genetic manipulation of flowering time in the chrysanthemum.

An RNA-Seq Transcriptome Analysis of Histone Modifiers and RNA Silencing Genes in Soybean during Floral Initiation Process

Epigenetics has been recognised to play vital roles in many plant developmental processes, including floral initiation through the epigenetic regulation of gene expression. The histone modifying proteins that mediate these modifications involve the SET domain-containing histone methyltransferases, JmjC domain-containing demethylase, acetylases and deacetylases. In addition, RNA interference (RNAi)-associated genes are also involved in epigenetic regulation via RNA-directed DNA methylation and post-transcriptional gene silencing. Soybean, a major crop legume, requires a short day to induce flowering. How histone modifications regulate the plant response to external cues that initiate flowering is still largely unknown. Here, we used RNA-seq to address the dynamics of transcripts that are potentially involved in the epigenetic programming and RNAi mediated gene silencing during the floral initiation of soybean. Soybean is a paleopolyploid that has been subjected to at least two rounds of whole genome duplication events. We report that the expanded genomic repertoire of histone modifiers and RNA silencing genes in soybean includes 14 histone acetyltransferases, 24 histone deacetylases, 47 histone methyltransferases, 15 protein arginine methyltransferases, 24 JmjC domain-containing demethylases and 47 RNAi-associated genes. To investigate the role of these histone modifiers and RNA silencing genes during floral initiation, we compared the transcriptional dynamics of the leaf and shoot apical meristem at different time points after a short-day treatment. Our data reveal that the extensive activation of genes that are usually involved in the epigenetic programming and RNAi gene silencing in the soybean shoot apical meristem are reprogrammed for floral development following an exposure to inductive conditions.

Identification and characterization of FaSOC1, a homolog of SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 from strawberry

A MADS-box gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) integrates multiple flowering signals to regulate floral transition in Arabidopsis. Strawberry (Fragaria spp.) is an economically important fruit crop, but its molecular control of flowering is largely unknown. In this study, a SOC1-like gene, FaSOC1, was isolated and characterized from strawberry. The open reading frame of FaSOC1 was 648bp, encoding a protein of 215 amino acids. Sequence alignment and phylogenetic analysis showed that the FaSOC1 protein contained a highly conserved MADS domain and a SOC1 motif, and that it was a member of the SOC1-like genes of dicots. The FaSOC1 protein mainly localized in the cytoplasm of onion epidermal cells and Arabidopsis protoplasts, and showed no transcriptional activation activity in yeast cells. Under the floral induction conditions, the expression of FaSOC1 increased during the first 2weeks of short-day treatment, but declined dramatically during three to 4weeks. FaSOC1 was highly expressed in reproductive organs, including shoot apices, floral buds, flowers, stamens and sepals. Overexpression of FaSOC1 in wild-type Arabidopsis caused early flowering and upregulated the expression of flowering time genes LFY and AP1. In addition, the yeast two-hybrid and BiFC assays confirmed that FaSOC1 could interact with AGL24. In conclusion, these results suggest that FaSOC1 is a flowering promoter in strawberry.

Stress and salicylic acid induce the expression of PnFT2 in the regulation of the stress-induced flowering of Pharbitis nil

Poor nutrition and low temperature stress treatments induced flowering in the Japanese morning glory Pharbitis nil (synonym Ipomoea nil) cv. Violet. The expression of PnFT2, one of two homologs of the floral pathway integrator gene FLOWERING LOCUS T (FT), was induced by stress, whereas the expression of both PnFT1 and PnFT2 was induced by a short-day treatment. There was no positive correlation between the flowering response and the homolog expression of another floral pathway integrator gene SUPPRESSOR OF OVEREXPRESSION OF CO1 and genes upstream of PnFT, such as CONSTANS. In another cultivar, Tendan, flowering and PnFT2 expression were not induced by poor nutrition stress. Aminooxyacetic acid (AOA), a phenylalanine ammonia-lyase inhibitor, inhibited the flowering and PnFT2 expression induced by poor nutrition stress in Violet. Salicylic acid (SA) eliminated the inhibitory effects of AOA. SA enhanced PnFT2 expression under the poor nutrition stress but not under non-stress conditions. These results suggest that SA induces PnFT2 expression, which in turn induces flowering; SA on its own, however, may not be sufficient for induction.

Morphological, Physiological, and Biochemical Changes inVitisGenotypes in Response to Photoperiod Regimes

The purpose of this study was to identify morphological, physiological, and biochemical changes in Vitis genotypes in response to photoperiod regimes. Experiments were conducted under greenhouse conditions using cold-sensitive Cabernet franc ( Vitis vinifera ) and cold-tolerant Couderc 3309 (3309C, V. riparia × V. rupestris ) and Concord ( V. labruscana ). Potted vines were exposed to short day (SD) (8 hr) or long day (LD) (16 hr) for 4, 6, and 8 weeks. Shoot growth, periderm formation, dormancy, freezing tolerance (lethal temperature that kills 50% of primary buds: LT50), and soluble sugar concentrations in leaf and bud tissues were examined. Shoot growth slowed in all cultivars under SD accompanied with increased periderm formation and dormancy depth. Concord initiated these changes first, followed by 3309C, then Cabernet franc. The three cultivars did not show differences in freezing tolerance under LD, with LT50 ranging between −6.1 and −8.1°C. However, freezing tolerance increased by 0.7, 2.0, and 2.7°C after 4, 6, and 8 weeks under SD, respectively. Freezing tolerance of Concord increased after 4 weeks of SD treatment, whereas that of 3309C and Cabernet franc did not increase until after 6 weeks of SD treatment. Among all sugars, raffinose had distinctive responses associated with photoperiod, remaining low and similar (0.5 to 2.3 mg/g dry weight) under LD. Under SD, raffinose concentration was generally higher, ranging from 2.2 to 5.7 mg/g dry weight in leaves and 1.6 to 3.7 mg/g dry weight in buds, with cold-tolerant 3309C and Concord accumulating higher concentrations compared to cold-sensitive Cabernet franc. These results suggest that raffinose accumulation might be an early step in response to photoperiod coinciding with slowed shoot growth, the induction of endodormancy, and the initial acquisition of freezing tolerance.