Winter Dormancy Research Articles

Metabolites in Cherry Buds to Detect Winter Dormancy.

Winter dormancy is still a “black box” in phenological models, because it evades simple observation. This study presents the first step in the identification of suitable metabolites which could indicate the timing and length of dormancy phases for the sweet cherry cultivar ‘Summit’. Global metabolite profiling detected 445 named metabolites in flower buds, which can be assigned to different substance groups such as amino acids, carbohydrates, phytohormones, lipids, nucleotides, peptides and some secondary metabolites. During the phases of endo- and ecodormancy, the energy metabolism in the form of glycolysis and the tricarboxylic acid (TCA) cycle was shut down to a minimum. However, the beginning of ontogenetic development was closely related to the up-regulation of the carbohydrate metabolism and thus to the generation of energy for the growth and development of the sweet cherry buds. From the 445 metabolites found in cherry buds, seven were selected which could be suitable markers for the ecodormancy phase, whose duration is limited by the date of endodormancy release (t1) and the beginning of ontogenetic development (t1*). With the exception of abscisic acid (ABA), which has been proven to control bud dormancy, all of these metabolites show nearly constant intensity during this phase.

Hybrid RNA Sequencing Strategy for the Dynamic Transcriptomes of Winter Dormancy in an Evergreen Herbaceous Perennial, Iris japonica.

Japanese iris (Iris japonica) is a popular perennial ornamental that originated in China; it has a long display period and remains green outdoors throughout the year. winter dormancy characteristics contribute greatly to the evergreenness of herbaceous perennials. Thus, it is crucial to explore the mechanism of winter dormancy in this evergreen herbaceous perennial. Here, we used the hybrid RNA-seq strategy including single-molecule real-time (SMRT) and next-generation sequencing (NGS) technologies to generate large-scale Full-length transcripts to examine the shoot apical meristems of Japanese iris. A total of 10.57 Gb clean data for SMRT and over 142 Gb clean data for NGS were generated. Using hybrid error correction, 58,654 full-length transcripts were acquired and comprehensively analysed, and their expression levels were validated by real-time qPCR. This is the first full-length RNA-seq study in the Iris genus; our results provide a valuable resource and improve understanding of RNA processing in this genus, for which little genomic information is available as yet. In addition, our data will facilitate in-depth analyses of winter dormancy mechanisms in herbaceous perennials, especially evergreen monocotyledons.

Influence of post-application irrigation and soil surfactants on tebuconazole efficacy against spring dead spot

Spring dead spot (SDS) (Ophiosphaerella spp.) causes damage to hybrid bermudagrass (Cynodon dactylon (L.) Pers. x transvaalensis Burtt Davy) grown in areas where winter dormancy occurs. The pathogen infects the stolons, rhizomes, and roots of warm-season grasses. Symptoms appear as circular, necrotic patches at spring greenup that reduce the playability and aesthetics of bermudagrass. Historically, fungicide efficacy against SDS has been inconsistent. There may be opportunities to improve application and post-application practices to mitigate the inconsistency. A study was conducted from 2019 to 2021 to examine the influence of post-application irrigation and soil surfactant on tebuconazole efficacy against SDS. The study was conducted at three locations: Virginia Tech Turfgrass Research Center (TRC), Blacksburg, VA; Independence Golf Club (IGC), Midlothian, VA; Nutters Crossing Golf Club (NCGC), Salisbury, MD. Tebuconazole was applied in the fall either once at 1.5 kg ai ha−1 or twice at 1.5 kg ai ha−1 two to four weeks apart when soil temperatures were between 10.7 and 21.8 °C. Treatments were applied with or without a soil surfactant and with or without 0.6 cm of post-application irrigation. Bermudagrass was assessed the following spring two or three times for patch number and percent SDS. Data were analyzed by assessment date, subjected to analysis of variance, and means were separated using Tukey's Honest Significant Difference test (P = 0.05). There were no treatment differences at IGC or NCGC in 2020 or 2021. At the TRC in both 2020 and 2021, results were inconsistent with tebuconazole generally suppressing SDS compared to the nontreated control. However, differences between tebuconazole-treated plots were variable. Our study suggests that including a soil surfactant with tebuconazole applications and/or irrigating post-application does not consistently increase SDS suppression.

Some introduction aspects of genus <i>Hoya</i> plants in greenhouse conditions

The paper deals with the study results of genus Hoya adaptive capabilities in protected ground conditions. The objects of the study are four species and one cultivar of the genus: Hoya cumingiana Decne., Hoya globulosa Hook. f., Hoya australis R. Br. ex Traill, Hoya pubicalyx Merrill, Hoya cv. Metallica . In culture, the life cycle of plant development corresponds to the natural one with minor periods of dormancy in autumn and winter associated with a reduction of daylight hours and insolation. For all introduced species, an increase of chlorophyll content and ratio of chlorophyll to flavonoids in the autumn period and minor fluctuations of flavonoids throughout the entire study period were noted, which indicates their relatively optimal nitrogen status. The author has revealed species specificity in the accumulation of chlorophyll and flavonoids and nitrogen balance. The shoot system is characterized by a plagiotropic growth direction and all its vegetative areas are structurally homogeneous. Each single-order stephanotis shoot grows at the top of the stem, shoots can be both short- and long-chamber. Intensive growth and decorativeness of the shoot system of H. globulosa , H. cumingiana and H. pubicalyx , the stability and plasticity of the photosynthetic apparatus provide the prospect of their use in phytodesign.

Evaluation of the frost tolerance of Hungarian-bred walnut cultivars

At present very few walnut cultivars can be said to be cosmopolitan cultivars, grown widely in the walnut-producing countries of the world. Walnut (Juglans regia L.) has poor ecological adaptability, as its cultivation is greatly influenced by low temperatures during the winter dormancy period and in early spring. The breeding activities conducted in various countries are therefore of great significance. Choosing suitable locations for cultivation is of key importance if optimum yield stability is to be achieved. The introduction of foreign walnut cultivars regularly runs into problems if, despite their high yielding ability, they are unable to adapt to the Hungarian climate. In Hungary the most critical weather events for walnuts are the frequent frosts in early spring. Buds therefore need to burst late to avoid damage to the flowers. Many papers have dealt with the frost tolerance of stone fruit, but only limited information has been published on the frost tolerance of walnut. For the first time in Hungary, artificial freezing tests were performed in the present work to determine the frost tolerance of the cultivars available in Hungary. The results could be of service to Hungarian growers in choosing the most suitable cultivar.

Evaluation of the frost tolerance of Hungarian-bred walnut cultivars

At present very few walnut cultivars can be said to be cosmopolitan cultivars, grown widely in the walnut-producing countries of the world. Walnut (Juglans regia L.) has poor ecological adaptability, as its cultivation is greatly influenced by low temperatures during the winter dormancy period and in early spring. The breeding activities conducted in various countries are therefore of great significance. Choosing suitable locations for cultivation is of key importance if optimum yield stability is to be achieved. The introduction of foreign walnut cultivars regularly runs into problems if, despite their high yielding ability, they are unable to adapt to the Hungarian climate. In Hungary the most critical weather events for walnuts are the frequent frosts in early spring. Buds therefore need to burst late to avoid damage to the flowers. Many papers have dealt with the frost tolerance of stone fruit, but only limited information has been published on the frost tolerance of walnut. For the first time in Hungary, artificial freezing tests were performed in the present work to determine the frost tolerance of the cultivars available in Hungary. The results could be of service to Hungarian growers in choosing the most suitable cultivar.

Leaf structural and physiological factors for winter dormancy color of zoysiagrass (Zoysia spp. Willd.)

Leaf structural and physiological factors for winter dormancy color of zoysiagrass (Zoysia spp. Willd.)

Changes of Endophytic Bacterial Community in Mature Leaves of Prunus laurocerasus L. during the Seasonal Transition from Winter Dormancy to Vegetative Growth.

Diverse communities of bacterial endophytes inhabit plant tissues, and these bacteria play important roles for plant growth and health. Cherry laurel (Prunus laurocerasus L.) is a broadleaf evergreen shrub that is widely grown in temperate zones for its ornamental and medicinal properties, however virtually nothing is known about its associated bacterial community. In this study, we analysed the matured one-year-old leaves of this plant using Illumina-based 16S rRNA gene metabarcoding to reveal the community structure of endophytic bacteria and understand its shifts during the seasonal transition from winter dormancy to a spring vegetative state. The overall community was composed of four dominant phyla (Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes). Corynebacterium, Acinetobacter, and Chryseobacterium genera were the most prevalent bacteria, comprising 13.3%, 6.9%, and 6.8% of the amplicon sequence variants (ASVs), respectively. The ASV richness and diversity increased significantly in May as compared to other sampling months (February, March, and April). We observed high variation in the overall community structure of endophytic bacteria among collection dates. The variation was only reflected by a few core community members, suggesting that the changes of the endophytic community during winter/spring seasonal transition are mostly associated with the less abundant community members. We identified biomarker taxa for late winter, mid spring, and late spring collection dates. This study is the first one to report on the diversity and composition of bacterial endophytes in the leaves of cherry laurel and its shifts across the dormancy-to-vegetative seasonal transition.

Cultivation and Fertility Practices Influence Hybrid Bermudagrass Recovery from Spring Dead Spot Damage

Spring dead spot (SDS), caused by Ophiosphaerella spp., is among the most damaging diseases to hybrid bermudagrass (Cynodon dactylon × transvaalensis) in areas where winter dormancy occurs. Management strategies that aid in turfgrass recovery from SDS damage have not been widely studied. An experiment was conducted in Blacksburg, VA, in 2019 and 2020, to determine the influence of various cultural practices on bermudagrass recovery from SDS damage. Fertility and cultivation were applied in the late spring/early summer, which is earlier than normal for cultivation practices for bermudagrass, to test their effectiveness in aiding bermudagrass recovery from SDS damage. The main effects of fertility and cultivation were arranged in a 2 × 3 factorial design with vertical mowing, solid-tine aerification, and no cultivation applied with urea (48.8 kg⋅ha−1 N) sprayed at trial initiation and 2 weeks later or without urea. Plots were assessed for the percent of SDS throughout the study. Data were analyzed as the percent change relative to the initial assessment to measure bermudagrass recovery. The main effect of fertility increased bermudagrass recovery from SDS damage in both 2019 and 2020. The main effects of vertical mowing and solid-tine aerification reduced bermudagrass recovery from SDS damage in 2020. These data suggest that two properly timed nitrogen fertilization applications at 48.8 kg⋅ha−1 optimized bermudagrass recovery from SDS damage, whereas late spring/early summer cultivation without fertility may inhibit bermudagrass recovery.

Adaptation of the regional agronomic diagnosis for grapevine yield analysis

Yield issues are crucial for winegrowers. In France, yield is often lower than winegrowers’ objectives, and there is a need to understand the causes and magnitude of yield variability in vineyard systems. The yield formation process for grapevine (Vitis vinifera) takes place over two consecutive years. Grapevine is also characterised by a limited control of phenology, a winter dormancy period and the existence of storage organs. We adapted the regional agronomic diagnosis approach as defined by Doré et al. (1997) to quantify grapevine yield variability in two complementary case studies. The regional agronomic diagnosis proved useful in acquiring knowledge on grapevine functioning, reflecting on the data collection strategy, and leveraging interventions to better control yield by integrating multiple factors, particularly in the context of transitioning viticulture systems. Furthermore, the successful application of a regional agronomic diagnosis to grapevine crops can be considered as a major contribution to increasing the understanding of yield formation. It helps winegrowers manage yield variability when addressing planned or unplanned changing conditions, such as an agroecological transition or climate change.

Time-Resolved Analysis of Candidate Gene Expression and Ambient Temperature During Bud Dormancy in Apple.

Winter dormancy – a period of low metabolic activity and no visible growth – appears as an adaptation to harsh winter conditions and can be divided into different phases. It is tightly controlled by environmental cues, with ambient temperature playing a major role. During endodormancy, a cultivar-specific amount of cold needs to be perceived, and during ecodormancy, heat hours accumulate before bud burst and anthesis in spring. Expression analysis, performed in several key fruit tree species, proved to be very useful in elucidating the molecular control of onset and release of dormancy. However, the time resolution of these experiments has been limited. Therefore, in this study, dense time-series expression analysis was conducted for 40 candidate genes involved in dormancy control, under the cool-temperate climate conditions in Dresden. Samples were taken from the cultivars ‘Pinova’ and ‘Gala,’ which differ in flowering time. The set of candidate genes included well-established dormancy genes such as DAM genes, MdFLC-like, MdICE1, MdPRE 1, and MdPIF4. Furthermore, we tested genes from dormancy-associated pathways including the brassinosteroid, gibberellic acid, abscisic acid (ABA), cytokinin response, and respiratory stress pathways. The expression patterns of well-established dormancy genes were confirmed and could be associated with specific dormancy phases. In addition, less well-known transcription factors and genes of the ABA signaling pathway showed associations with dormancy progression. The three ABA signaling genes HAB1_chr15, HAI3, and ABF2 showed a local minimum of gene expression in proximity of the endodormancy to ecodormancy transition. The number of sampling points allowed us to correlate expression values with temperature data, which revealed significant correlations of ambient temperature with the expression of the Malus domestica genes MdICE1, MdPIF4, MdFLC-like, HAB1chr15, and the type-B cytokinin response regulator BRR9. Interestingly, the slope of the linear correlation of temperature with the expression of MdPIF4 differed between cultivars. Whether the strength of inducibility of MdPIF4 expression by low temperature differs between the ‘Pinova’ and ‘Gala’ alleles needs to be tested further.

Adaptive management in a conservation breeding program: Mimicking habitat complexities facilitates reproductive success in narrow-headed gartersnakes (Thamnophis rufipunctatus).

Mimicking natural parameters and complexities in zoo conservation breeding programs can facilitate natural physiological and behavioral traits, which in turn can inform more effective species reintroduction efforts. To curtail population declines of threatened narrow-headed gartersnakes (Thamnophis rufipunctatus), the Arizona Center for Nature Conservation/Phoenix Zoo partnered with a multiagency conservation working group to develop an ex situ propagation-for-release program. Initially, Zoo staff followed common snake husbandry protocols of manually inducing brumation (i.e., winter dormancy). Copulation was observed during the first few years, but no births resulted. Also, some older individuals developed post-brumation health abnormalities, prompting a strategic reassessment. To facilitate propagation and improve health, Zoo staff applied ecological knowledge of T. rufipunctatus and an adaptive management strategy to implement key parameters for success: sociality, refugia, breeding and foraging behaviors, and natural brumation. Zoo staff developed a large multisnake enclosure that mimicked natural ecological and habitat complexities including a hibernaculum to stimulate natural brumation. Gartersnakes were left mostly unimpeded to conduct natural behaviors across seasons in the enriched environment. We referenced change in body mass after ten brumation periods as a proxy for health. Under natural brumation, gartersnakes did not lose body mass, and this shift resulted in fully ex situ parturition events-the first for this imperiled species. We highlight the efficacy of adaptive management and incorporation of natural parameters and environmental complexities into conservation breeding programs. These actions can improve the health and success of animals under managed care-processes applicable to a range of taxa targeted for conservation translocations.

Analysys of species diversity of ants (Hymenoptera: Formicidae) in Lviv (Ukraine)

Background. The paper presents the results of original research on the diversity of ants (Hymenoptera: Formicidae) in Lviv (Ukraine). In Ukraine, 146 species of ants from 39 genera of five subfamilies are known at present. Ants play an important role in ecosystems. They build their nests in the soil, which contributes to better soil formation. Ants are important links in trophic chains. They are the most adaptable to settling new territories. The diversity of ants in Lviv is potentially very high due to a good geographical location between Polissia and the Carpathians. However, today there are almost no articles on ants’ taxonomic groups in Lviv. This study aims to present new records of Lviv myrmecofauna, and to investigate ants’ seasonal rhythms. Materials and Methods. The objects of our research were ants (Formicidae), collected from three different park areas in Lviv, and the territories of the Botanical garden of Ivan Franko National University of Lviv between 2020 and 2021. Main sampling methods were hand collecting and usage of sweet baits (Romero, 1989). In addition, we investigated ants’ behavioral traits related to the winter dormancy state. Results and Discussion. We analyzed 90 samples of worker ants. In the course of identification, 20 different species belonging to seven genera (Formica Linnaeus, 1758, Lasius Fabricius, 1804, Camponotus Mayr, 1861, Myrmecina Curtis, 1829, Myrmica Latreille, 1804, Temnothorax Nylander, 1856 and Tetramorium Mayr, 1855) were found, which in turn belong to two subfamilies: Formicinae Lepeletier, 1836 and Myrmecinae Emery, 1877. Numerous species belong to genera Lasius, Formica, Myrmica, and Tetramorium, which are mentioned as common in Eastern Europe. Behavioral research related to hibernation shows that Formica polyctena Forster, 1850 begins to enter hibernation earlier than other species, namely on 30.09.21 at an average air temperature of +12 °C. They were the latest to leave this state, at the end of April 25.04.22 at the same temperature. On the other hand, Lasius niger (Linnaeus, 1758) remained active the longest in autumn, namely until 21.10.21 at a temperature of +3 °C, and came to the surface one of the earliest on 24.03.22 at +9 °C. Conclusion. We recorded 20 ant species that have not been mentioned for Lviv because of the absence of any published information. The data obtained within this study show the important role of botanical gardens in preserving the biodiversity of ants despite their small area. Therefore, the topic of the diversity of the myrmecofauna of Ukraine, and urban areas in particular, is relevant and insufficiently researched today.

The Identification of Small RNAs Differentially Expressed in Apple Buds Reveals a Potential Role of the Mir159-MYB Regulatory Module during Dormancy.

Winter dormancy is an adaptative mechanism that temperate and boreal trees have developed to protect their meristems against low temperatures. In apple trees (Malus domestica), cold temperatures induce bud dormancy at the end of summer/beginning of the fall. Apple buds stay dormant during winter until they are exposed to a period of cold, after which they can resume growth (budbreak) and initiate flowering in response to warmer temperatures in spring. It is well-known that small RNAs modulate temperature responses in many plant species, but however, how small RNAs are involved in genetic networks of temperature-mediated dormancy control in fruit tree species remains unclear. Here, we have made use of a recently developed ARGONAUTE (AGO)-purification technique to isolate small RNAs from apple buds. A small RNA-seq experiment resulted in the identification of 17 micro RNAs (miRNAs) that change their pattern of expression in apple buds during dormancy. Furthermore, the functional analysis of their predicted target genes suggests a main role of the 17 miRNAs in phenylpropanoid biosynthesis, gene regulation, plant development and growth, and response to stimulus. Finally, we studied the conservation of the Arabidopsis thaliana regulatory miR159-MYB module in apple in the context of the plant hormone abscisic acid homeostasis.

Use of Canopeo for Estimating Green Coverage of Bermudagrass during Postdormancy Regrowth

Objective methods of estimating green coverage using digital image analysis have been used increasingly by turfgrass scientists. The objective of our research was to evaluate the effectiveness of Canopeo, a relatively new smartphone application, for estimating green coverage of bermudagrass (Cynodon dactylon) emerging from winter dormancy, with or without colorants. A field study was conducted on a research ‘U3’ bermudagrass fairway in Stillwater, OK, during Spring 2019 and 2020. The experiment was conducted as a randomized complete block design with three colorant treatments: Endurant Fairway (FW), Endurant Perennial Ryegrass (PR), and an untreated control. Green coverage of the turfgrass canopy was determined weekly from mid-March to early May using a digital camera and ImageJ software, and a smartphone and the Canopeo application. Green coverage estimates from Canopeo correlated strongly (r = 0.91) with those from ImageJ when no colorants were applied. Correlation between Canopeo and ImageJ was diminished under plots treated with colorants. Canopeo is an effective tool for estimating green coverage of living turfgrasses, but additional calibration may be required for acceptable performance when evaluating greenness of colorant-treated turfgrasses.

Effect of Photoperiod, Propagative Material, and Production Period on Greenhouse-grown Ginger and Turmeric Plants

The objectives were to 1) compare growth and yield of different ginger (Zingiber officinale) and turmeric (Curcuma longa) propagules grown under two photoperiods (Expt. 1); and 2) evaluate whether their growing season could be extended with night interruption lighting (NI) during the winter (Expt. 2). In Expt. 1, propagules included 1) micropropagated tissue culture (TC) transplants, 2) second-generation rhizomes harvested from TC transplants (2GR), and 3) seed rhizomes (R). Plants received natural short days (SDs) or NI providing a total photon flux density (TPFD) of 1.3 µmol·m−2·s−1. Providing NI increased number of new tillers or leaves per plant, rhizome yield (i.e., rhizome fresh weight), and dry mass partitioning to rhizomes in both species. There was no clear trend on SPAD index in response to photoperiod or propagative material. Although TC-derived plants produced more tillers or leaves per plant, 2GR ginger and R turmeric produced a higher rhizome yield. In Expt. 2, seed rhizomes of ginger and turmeric were grown under five treatments with different photoperiods and/or production periods: 1) 20 weeks with NI (20NI), 2) 24 weeks with NI (24NI), 3) 28 weeks with NI (28NI), 4) 14 weeks with NI + 10 weeks under natural SDs (24NISD), and 5) 14 weeks with NI + 14 weeks under natural SDs (28NISD). NI provided a TPFD of 4.5 µmol·m−2·s−1. Lengthening the production period and providing NI increased rhizome yield and crude fiber content in both species. SPAD index decreased when plants were exposed to natural SDs at the end of the production period (NISD treatments). Results demonstrate the potential to overcome winter dormancy of ginger and turmeric plants with NI, enabling higher rhizome yield under natural SDs.

Phenological Stages of Development of Cornus L. S. Str. Species (Cornaceae) According to BBCH Scale

Under conditions of pronounced dynamic climate change, the scope of phenological data is constantly expanding and increasingly extends beyond local regions. For the international integration of phenological research, a standardized description of the stages of plant development and their identical coding is used – the BBCH scale (Biologische Bundesanstalt, Bundessortenamt und CHemische Industrie). Phenophases of seasonal development, according to BBCH, are already unified for many different in origin, nature of ecology, and economic use of plants of common and little-known species and crops, including fruit. According to the BBCH scale, we described the seasonal stages of development of 23 cultivars of Cornus mas L. selection gene pool of the M.M. Gryshko National Botanical Garden of the National Academy of Sciences of Ukraine, genotypes of C. officinalis Siebold & Zucc., nine genotypes of C. sessilis Torr. ex Durand, as well as three genotypes of the artificial hybrid from crossing C. officinalis × C. mas. Phenological monitoring was carried out in NBG (Ukraine) two or three times a week for three seasons (2018–2020) from the beginning of vegetation (bud development) to November and the beginning of winter dormancy. In the studied species of the subgenus Cornus, as in some other stone fruit plants, there are eight of the ten main stages of seasonal development. In all studied species and cultivars of dogwood at the beginning of the growing season generative buds in their development significantly ahead of vegetative and plants begin seasonal development from the development of inflorescences and flowering (principal growth stage 5 and principal growth stage 6, respectively). Different species and varieties differ in the calendar dates of onset and duration of certain major stages of development. The obtained data are important for further studies of adaptive capabilities of Cornus species and cultivars in different climatic conditions, for practical use of genetic resources of studied Cornus species and cultivars, as well as for the introduction of little-known Cornus species and their use in agricultural production, pharmacology, ornamental and landscape gardens.

Seasonal dynamics and optimal diagnostics of Grapevine red blotch virus in a British Columbian vineyard

Tracking the occurrence and spread of Grapevine red blotch virus (GRBV) depends on robust and reliable diagnostics. Tissue sampling strategy and optimal choice of molecular test are critical for diagnostic success. This study investigated GRBV titres from several grapevine tissues, including roots, buds, cortical scrapings, and leaves, at varying distances from the cordons, and at different times during the growing season and winter dormancy. Two common nucleic acid extraction techniques were compared, a low-cost high-throughput nucleic acid extraction method (GES) and a DNA column purification method. Optimal combinations of sampling parameters were determined for summer and winter diagnostics. In dormant samples, cortical scrapings yielded the highest GRBV titres and produced no false-negatives. In summer samples, basal leaves yielded high GRBV titres throughout the summer months, with only one false negative on the earliest sample date. These two tissues provide the best samples for reliable and reproducible GRBV diagnostics. The crude GES and DNA column purification methods performed comparably well for binary diagnostics, however, the GES method performed poorly in quantitative analysis.

MADS-box transcription factors determine the duration of temporary winter dormancy in closely related evergreen and deciduous Iris spp.

Winter dormancy (WD) is a crucial strategy for plants coping with potentially deadly environments. In recent decades, this process has been extensively studied in economically important perennial eudicots due to changing climate. However, in evergreen monocots with no chilling requirements, dormancy processes are so far a mystery. In this study, we compared the WD process in closely related evergreen (Iris japonica) and deciduous (I. tectorum) iris species across crucial developmental time points. Both iris species exhibit a 'temporary' WD process with distinct durations, and could easily resume growth under warm conditions. To decipher transcriptional changes, full-length sequencing for evergreen iris and short read RNA sequencing for deciduous iris were applied to generate respective reference transcriptomes. Combining results from a multipronged approach, SHORT VEGETATIVE PHASE and FRUITFULL (FUL) from MADS-box was associated with a dormancy- and a growth-related module, respectively. They were co-expressed with genes involved in phytohormone signaling, carbohydrate metabolism, and environmental adaptation. Also, gene expression patterns and physiological changes in the above pathways highlighted potential abscisic acid and jasmonic acid antagonism in coordinating growth and stress responses, whereas differences in carbohydrate metabolism and reactive oxygen species scavenging might lead to species-specific WD durations. Moreover, a detailed analysis of MIKCCMADS-box in irises revealed common features described in eudicots as well as possible new roles for monocots during temporary WD, such as FLOWERING LOCUS C and FUL. In essence, our results not only provide a portrait of temporary WD in perennial monocots but also offer new insights into the regulatory mechanism underlying WD in plants.

Temporal expression study of miRNAs in the crown tissues of winter wheat grown under natural growth conditions

BackgroundWinter wheat requires prolonged exposure to low temperature to initiate flowering (vernalization). Shoot apical meristem of the crown is the site of cold perception, which produces leaf primordia during vegetative growth before developing into floral primordia at the initiation of the reproductive phase. Although many essential genes for winter wheat cold acclimation and floral initiation have been revealed, the importance of microRNA (miRNA) meditated post-transcriptional regulation in crowns is not well understood. To understand the potential roles of miRNAs in crown tissues, we performed a temporal expression study of miRNAs in crown tissues at the three-leaf stage, winter dormancy stage, spring green-up stage, and jointing stage of winter wheat grown under natural growth conditions.ResultsIn total, 348 miRNAs belonging to 298 miRNA families, were identified in wheat crown tissues. Among them, 92 differentially expressed miRNAs (DEMs) were found to be significantly regulated from the three-leaf stage to the jointing stage. Most of these DEMs were highly expressed at the three-leaf stage and winter dormancy stage, and then declined in later stages. Six DEMs, including miR156a-5p were markedly induced during the winter dormancy stage. Eleven DEMs, including miR159a.1, miR390a-5p, miR393-5p, miR160a-5p, and miR1436, were highly expressed at the green-up stage. Twelve DEMs, such as miR172a-5p, miR394a, miR319b-3p, and miR9676-5p were highly induced at the jointing stage. Moreover, 14 novel target genes of nine wheat or Pooideae-specific miRNAs were verified using RLM-5′ RACE assay. Notably, six mTERFs and two Rf1 genes, which are associated with mitochondrial gene expression, were confirmed as targets of three wheat-specific miRNAs.ConclusionsThe present study not only confirmed the known miRNAs associated with phase transition and floral development, but also identified a number of wheat or Pooideae-specific miRNAs critical for winter wheat cold acclimation and floral development. Most importantly, this study provided experimental evidence that miRNA could regulate mitochondrial gene expression by targeting mTERF and Rf1 genes. Our study provides valuable information for further exploration of the mechanism of miRNA mediated post-transcriptional regulation during winter wheat vernalization and inflorescent initiation.