Release Of Buds Research Articles

Why can Mikania micrantha cover trees quickly during invasion?

The invasion of Mikania micrantha by climbing and covering trees has rapidly caused the death of many shrubs and trees, seriously endangering forest biodiversity. In this study, M. micrantha seedlings were planted together with local tree species (Cryptocarya concinna) to simulate the process of M. micrantha climbing under the forest. We found that the upper part of the M. micrantha stem lost its support after climbing to the top of the tree, grew in a turning and creeping manner, and then grew branches rapidly to cover the tree canopy. Then, we simulated the branching process through turning treatment. We found that a large number of branches had been formed near the turning part of the M. micrantha stem (TP). Compared with the upper part of the main stem (UP), the contents of plant hormones (auxin, cytokinin, gibberellin), soluble sugars (sucrose, glucose, fructose) and trehalose-6-phosphate (T6P) were significantly accumulated at TP. Further combining the transcriptome data of different parts of the main stem under erect or turning treatment, a hypothetical regulation model to illustrate how M. micrantha can quickly cover trees was proposed based on the regulation of sugars and hormones on plant branching; that is, the lack of support after ascending the top of the tree led to turning growth of the main stem, and the enhancement of sugars and T6P levels in the TP may first drive the release of nearby dormant buds. Plant hormone accumulation may regulate the entrance of buds into sustained growth and maintain the elongation of branches together with sugars to successfully covering trees.

Characterization of the MIKCC-type MADS-box gene family in blueberry and its possible mechanism for regulating flowering in response to the chilling requirement.

The expression peak of VcAP1.4, VcAP1.6, VcAP3.1, VcAP3.2, VcAG3, VcFLC2, and VcSVP9 coincided with the endo-dormancy release of flower buds. Additionally, GA4+7 not only increased the expression of these genes but also promoted flower bud endo-dormancy release. The MIKCC-type MADS-box gene family is involved in the regulation of flower development. A total of 109 members of the MIKCC-type MADS-box gene family were identified in blueberry. According to the phylogenetic tree, these 109 MIKCC-type MADS-box proteins were divided into 13 subfamilies, which were distributed across 40 Scaffolds. The results of the conserved motif analysis showed that among 20 motifs, motifs 1, 3, and 9 formed the MADS-box structural domain, while motifs 2, 4, and 6 formed the K-box structural domain. The presence of 66 pairs of fragment duplication events in blueberry suggested that gene duplication events contributed to gene expansion and functional differentiation. Additionally, the presence of cis-acting elements revealed that VcFLC2, VcAG3, and VcSVP9 might have significant roles in the endo-dormancy release of flower buds. Meanwhile, under chilling conditions, VcAP3.1 and VcAG7 might facilitate flower bud dormancy release. VcSEP11 might promote flowering following the release of endo-dormancy, while the elevated expression of VcAP1.7 (DAM) could impede the endo-dormancy release of flower buds. The effect of gibberellin (GA4+7) treatment on the expression pattern of MIKCC-type MADS-box genes revealed that VcAP1.4, VcAP1.6, VcAP3.1, VcAG3, and VcFLC2 might promote flower bud endo-dormancy release, while VcAP3.2, VcSEP11, and VcSVP9 might inhibit its endo-dormancy release. These results indicated that VcAP1.4, VcAP1.6, VcAP1.7 (DAM), VcAP3.1, VcAG3, VcAG7, VcFLC2, and VcSVP9 could be selected as key regulatory promoting genes for controlling the endo-dormancy of blueberry flower buds.

GPIbα–filamin A interaction regulates megakaryocyte localization and budding during platelet biogenesis

AbstractGlycoprotein Ibα (GPIbα) is expressed on the surface of platelets and megakaryocytes (MKs) and anchored to the membrane skeleton by filamin A (flnA). Although GPIb and flnA have fundamental roles in platelet biogenesis, the nature of this interaction in megakaryocyte biology remains ill-defined. We generated a mouse model expressing either human wild-type (WT) GPIbα (hGPIbαWT) or a flnA-binding mutant (hGPIbαFW) and lacking endogenous mouse GPIbα. Mice expressing the mutant GPIbα transgene exhibited macrothrombocytopenia with preserved GPIb surface expression. Platelet clearance was normal and differentiation of MKs to proplatelets was unimpaired in hGPIbαFW mice. The most striking abnormalities in hGPIbαFW MKs were the defective formation of the demarcation membrane system (DMS) and the redistribution of flnA from the cytoplasm to the peripheral margin of MKs. These abnormalities led to disorganized internal MK membranes and the generation of enlarged megakaryocyte membrane buds. The defective flnA-GPIbα interaction also resulted in misdirected release of buds away from the vasculature into bone marrow interstitium. Restoring the linkage between flnA and GPIbα corrected the flnA redistribution within MKs and DMS ultrastructural defects as well as restored normal bud size and release into sinusoids. These studies define a new mechanism of macrothrombocytopenia resulting from dysregulated MK budding. The link between flnA and GPIbα is not essential for the MK budding process, however, it plays a major role in regulating the structure of the DMS, bud morphogenesis, and the localized release of buds into the circulation.

Comparative transcriptome analysis of genes involved in paradormant bud release response in 'Summer Black' grape.

Grapevines possess a hierarchy of buds, and the fruitful winter bud forms the foundation of the two-crop-a-year cultivation system, yielding biannual harvests. Throughout its developmental stages, the winter bud sequentially undergoes paradormancy, endodormancy, and ecodormancy to ensure survival in challenging environmental conditions. Releasing the endodormancy of winter bud results in the first crop yield, while breaking the paradormancy of winter bud allows for the second crop harvest. Hydrogen cyanamide serves as an agent to break endodormancy, which counteracting the inhibitory effects of ABA, while H2O2 and ethylene function as signaling molecules in the process of endodormancy release. In the context of breaking paradormancy, common agronomic practices include short pruning and hydrogen cyanamide treatment. However, the mechanism of hydrogen cyanamide contributes to this process remains unknown. This study confirms that hydrogen cyanamide treatment significantly improved both the speed and uniformity of bud sprouting, while short pruning proved to be an effective method for releasing paradormancy until August. This observation highlights the role of apical dominance as a primary inhibitory factor in suppressing the sprouting of paradormant winter bud. Comparative transcriptome analysis revealed that the sixth node winter bud convert to apical tissue following short pruning and established a polar auxin transport canal through the upregulated expression of VvPIN3 and VvTIR1. Moreover, short pruning induced the generation of reactive oxygen species, and wounding, ethylene, and H2O2 collectively acted as stimulating signals and amplified effects through the MAPK cascade. In contrast, hydrogen cyanamide treatment directly disrupted mitochondrial function, resulting in ROS production and an extended efficacy of the growth hormone signaling pathway induction.

Colon-Adhering Delivery System with Inflammation Responsiveness for Localized Therapy of Experimental Colitis.

Ulcerative colitis (UC) is a chronic inflammation-related disease that severely affects the colon and rectum regions. A variety of therapy regimens are used for the treatment of UC. Clinically, therapeutic enema is the choice of therapy for UC patients. Irrespective of on-site administration, the major limitation of therapeutic enemas is the dispossession of the medicine followed by low drug availability for the therapeutic action. In our present work, we have developed an enzyme-responsive injectable hydrogel (ER-hydrogel) to overcome the limitations of therapeutic enema. The hydrogels possess two major advantages, which are being exploited for therapeutic drug delivery in UC: prolonged retention and enzyme responsiveness. The former is one of the prominent advantages of hydrogel compared to free drug enema and the latter controls the release of the drug or provides drug release on-demand. The ER-hydrogel was formulated by the heat-cool method and for therapeutic purposes, a corticosteroid drug, budesonide (Bud), was encapsulated into the ER-hydrogel and evaluated for its various physicochemical and therapeutic potentials in dextran sodium sulfate (DSS)-induced UC. In vitro and ex vivo adhesion studies confirm the retention or mucoadhesive nature of the ER-hydrogel, and the upsurge in Bud release from the Bud-loaded ER-hydrogel upon the addition of esterase enzyme confirms the enzyme-mediated drug release from the ER-hydrogel. Moreover, Bud-loaded ER-hydrogel exhibited promising results in alleviating the disease activity index of UC, and restored the length of the colon, which is the main hallmark of UC. In terms of the health of the colon tissue, the Bud-loaded ER-hydrogel restored the colonic tissue damage, as seen in the H&E-stained, AB-NR-stained, and HID-AB-stained colon sections. Finally, the Bud-loaded ER-hydrogel also markedly subsided the IL-1β, TNF-α, MPO, and nitrite levels in serum and colon tissues. Thus, the fabricated Bud-loaded ER-hydrogel possesses appreciable translational potential due to its ability to significantly ameliorate inflammatory changes compared to naive or water-based therapeutic enema in acute experimental colitis in mice.

Shoot buds of subtropical running bamboos demonstrate endodormancy and chilling requirements for their release

Bamboos, widely distributed in tropical and subtropical regions and significant in ecological, economic and cultural values, are similar to trees in the above-ground growth and to geophytes in the below-ground structure. However, contrary to well-studied endodormancy and the related chilling requirement that synchronize the seasonal development of above-ground buds of tree species and the well-studied below-ground buds of geophytes, it is unknown whether bamboos demonstrate the endodormancy and chilling requirements as those of trees and geophytes, which limits our understanding of how bamboos phenology cope with climate change. Our work mainly examined the effect of temperature on the dormancy release of underground shoot buds of two important subtropical running bamboo species, Lei bamboo (Phyllostachys violascens) and Moso bamboo (Phyllostachys edulis). In the experiments, the bamboo seedlings were first subjected to different durations of natural chilling and subsequently to a regrowth test under high-temperature forcing conditions in whole-tree chambers. In the regrowth test the dormancy state of the shoot buds was examined by observing shoot development, i.e., the emergence of the new shoot aboveground, a significant spring phenological event in many bamboo species. The time required for shooting under the forcing conditions decreased with prolonged chilling, indicating that the shoot buds of these two bamboo species demonstrate the phenomena of endodormancy and a chilling requirement for endodormancy release. For Lei bamboo, the chilling requirement was estimated as 45 Chill Portions (CP) and heat requirement was 9978 ± 6713 GDH℃. As for Moso bamboo, the estimated chilling requirement was 35CP and heat requirement was 6713 ± 3087 GDH℃. Meanwhile, the Vegis effect (an interaction of previous chilling accumulation and forcing temperature) was also found in Lei bamboo: there was a large difference in the time required for shoot development between low and high forcing temperatures after short durations of chilling, but the difference decreased with prolonged chilling. It was also shown that bamboo shoot buds almost received the same heat requirements for emergence at different forcing temperatures under the same chilling requirements. Our results will improve the understanding of temperature regulation of spring phenology in subtropical bamboo forests and promote bamboo production and management.

The bud awakens: Interplay among hormones and sugar controls bud release.

The bud awakens: Interplay among hormones and sugar controls bud release.

Small RNA and Degradome Sequencing in Floral Bud Reveal Roles of miRNAs in Dormancy Release of Chimonanthus praecox.

Chimonanthus praecox (wintersweet) is highly valued ornamentally and economically. Floral bud dormancy is an important biological characteristic in the life cycle of wintersweet, and a certain period of chilling accumulation is necessary for breaking floral bud dormancy. Understanding the mechanism of floral bud dormancy release is essential for developing measures against the effects of global warming. miRNAs play important roles in low-temperature regulation of flower bud dormancy through mechanisms that are unclear. In this study, small RNA and degradome sequencing were performed for wintersweet floral buds in dormancy and break stages for the first time. Small RNA sequencing identified 862 known and 402 novel miRNAs; 23 differentially expressed miRNAs (10 known and 13 novel) were screened via comparative analysis of breaking and other dormant floral bud samples. Degradome sequencing identified 1707 target genes of 21 differentially expressed miRNAs. The annotations of the predicted target genes showed that these miRNAs were mainly involved in the regulation of phytohormone metabolism and signal transduction, epigenetic modification, transcription factors, amino acid metabolism, and stress response, etc., during the dormancy release of wintersweet floral buds. These data provide an important foundation for further research on the mechanism of floral bud dormancy in wintersweet.

Auxin-independent effects of apical dominance induce changes in phytohormones correlated with bud outgrowth.

The inhibition of shoot branching by the growing shoot tip of plants, termed apical dominance, was originally thought to be mediated by auxin. Recently, the importance of the shoot tip sink strength during apical dominance has re-emerged with recent studies highlighting roles for sugars in promoting branching. This raises many unanswered questions on the relative roles of auxin and sugars in apical dominance. Here we show that auxin depletion after decapitation is not always the initial trigger of rapid cytokinin (CK) increases in buds that are instead correlated with enhanced sugars. Auxin may also act through strigolactones (SLs) which have been shown to suppress branching after decapitation, but here we show that SLs do not have a significant effect on initial bud outgrowth after decapitation. We report here that when sucrose or CK is abundant, SLs are less inhibitory during the bud release stage compared to during later stages and that SL treatment rapidly inhibits CK accumulation in pea (Pisum sativum) axillary buds of intact plants. After initial bud release, we find an important role of gibberellin (GA) in promoting sustained bud growth downstream of auxin. We are, therefore, able to suggest a model of apical dominance that integrates auxin, sucrose, SLs, CKs, and GAs and describes differences in signalling across stages of bud release to sustained growth.

Widely targeted metabolite profiling of mango stem apex during floral induction by compond of mepiquat chloride, prohexadione-calcium and uniconazole.

Insufficient low temperatures in winter and soil residues caused by paclobutrazol (PBZ) application pose a considerable challenge for mango floral induction (FI). Gibberellin inhibitors SPD (compound of mepiquat chloride, prohexadione-calcium and uniconazole) had a significant influence on enhancing the flowering rate and yield of mango for two consecutive years (2020-2021). Researchers have indicated that FI is regulated at the metabolic level; however, little is known about the metabolic changes during FI in response to SPD treatment. Here, ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS)-based widely targeted metabolomic analysis was carried out to assess the metabolic differences in the mango stem apex during different stage of mango FI (30, 80, 100 days after SPD/water treatment). A total of 582 compounds were annotated and 372 metabolites showed two-fold differences in abundance (variable importance in projection, VIP ≥ 1 and fold change, FC≥ 2 or≤ 0.5) between buds at 30, 80, 100 days after SPD/water treatment or between buds under different treatment. Lipids, phenolic acids, amino acids, carbohydrates, and vitamins were among metabolites showing significant differences over time after SPD treatment. Here, 18 out of 20 lipids, including the lysophosphatidylethanolamine (12, LPE), lysophosphatidylcholine (7, LPC), and free fatty acids (1, FA), were significantly upregulated from 80 to 100 days after SPD treatment comared to water treatment. Meanwhile, the dormancy release of mango buds from 80 to 100 days after SPD treatment was accompanied by the accumulation of proline, ascorbic acid, carbohydrates, and tannins. In addition, metabolites, such as L-homocysteine, L-histidine, and L-homomethionine, showed more than a ten-fold difference in relative abundance from 30 to 100 days after SPD treatment, however, there were no significant changes after water treatment. The present study reveals novel metabolites involved in mango FI in response to SPD, which would provide a theoretical basis for utilizing SPD to induce mango flowering.

PpMAPK6 regulates peach bud endodormancy release through interactions with PpDAM6

The MADS-box (DAM) gene PpDAM6, which is related to dormancy, plays a key role in bud endodormancy release, and the expression of PpDAM6 decreases during endodormancy release. However, the interaction network that governs its regulation of the endodormancy release of flower buds in peach remains unclear. In this study, we used yeast two-hybrid (Y2H) assays to identify a mitogen-activated protein kinase, PpMAPK6, that interacts with PpDAM6 in a peach dormancy-associated SSHcDNA library. PpMAPK6 is primarily located in the nucleus, and Y2H and bimolecular fluorescence complementation (BiFC) assays verified that PpMAPK6 interacts with PpDAM6 by binding to the MADS-box domain of PpDAM6. Quantitative real-time PCR (qRT-PCR) analysis showed that the expression of PpMAPK6 was opposite that of PpDAM6 in the endodormancy release of three cultivars with different chilling requirements (Prunus persica ‘Chunjie’, Prunus persica var. nectarina ‘Zhongyou 5’, Prunus persica ‘Qingzhou peach’). In addition, abscisic acid (ABA) inhibited the expression of PpMAPK6 and promoted the expression of PpDAM6 in flower buds. The results indicated that PpMAPK6 might phosphorylate PpDAM6 to accelerate its degradation by interacting with PpDAM6. The expression of PpMAPK6 increased with decreasing ABA content during endodormancy release in peach flower buds, which in turn decreased the expression of PpDAM6 and promoted endodormancy release.

Phytoplasma Infection Blocks Starch Breakdown and Triggers Chloroplast Degradation, Leading to Premature Leaf Senescence, Sucrose Reallocation, and Spatiotemporal Redistribution of Phytohormones.

Witches’-broom (WB, excessive initiation, and outgrowth of axillary buds) is one of the remarkable symptoms in plants caused by phytoplasmas, minute wall-less intracellular bacteria. In healthy plants, axillary bud initiation and outgrowth are regulated by an intricate interplay of nutrients (such as sugars), hormones, and environmental factors. However, how these factors are involved in the induction of WB by phytoplasma is poorly understood. We postulated that the WB symptom is a manifestation of the pathologically induced redistribution of sugar and phytohormones. Employing potato purple top phytoplasma and its alternative host tomato (Solanum lycopersicum), sugar metabolism and transportation, and the spatiotemporal distribution of phytohormones were investigated. A transmission electron microscopy (TEM) analysis revealed that starch breakdown was inhibited, resulting in the degradation of damaged chloroplasts, and in turn, premature leaf senescence. In the infected source leaves, two marker genes encoding asparagine synthetase (Sl-ASN) and trehalose-6-phosphate synthase (Sl-TPS) that induce early leaf senescence were significantly up-regulated. However, the key gibberellin biosynthesis gene that encodes ent-kaurene synthase (Sl-KS) was suppressed. The assessment of sugar content in various infected tissues (mature leaves, stems, roots, and leaf axils) indicated that sucrose transportation through phloem was impeded, leading to sucrose reallocation into the leaf axils. Excessive callose deposition and the resulting reduction in sieve pore size revealed by aniline blue staining and TEM provided additional evidence to support impaired sugar transport. In addition, a spatiotemporal distribution study of cytokinin and auxin using reporter lines detected a cytokinin signal in leaf axils where the axillary buds initiated. However, the auxin responsive signal was rarely present in such leaf axils, but at the tips of the newly elongated buds. These results suggested that redistributed sucrose as well as cytokinin in leaf axils triggered the axillary bud initiation, and auxin played a role in the bud elongation. The expression profiles of genes encoding squamosa promoter-binding proteins (Sl-SBP1), and BRANCHED1 (Sl-BRC1a and Sl-BRC1b) that control axillary bud release, as determined by quantitative reverse transcription (qRT)-PCR, indicated their roles in WB induction. However, their interactions with sugars and cytokinins require further study. Our findings provide a comprehensive insight into the mechanisms by which phytoplasmas induce WB along with leaf chlorosis, little leaf, and stunted growth.

Preanthesis changes in freeze resistance, relative water content, and ovary growth preempt bud phenology and signify dormancy release of sour cherry floral buds.

Growing degree hours (GDH) predicted floral bud development of 'Montmorency' sour cherry and explained changes in lethal temperatures (LT50) that preempted any visible changes in bud phenology. The gradual warming during late winter and early spring promotes floral bud development and, concomitantly, the de-acclimation of Prunus sp. flowers. In fact, once ecodormancy releases, an approximate 20°C loss of hardiness occurs prior to any distinguishable changes in external bud phenology. The aim of the following work was to characterize the physiological changes of 'Montmorency' sour cherry floral buds as they transition from endo- and ecodormancy and resume growth, and to determine whether physiological and anatomical characteristics within the buds preempt or signify dormancy release to enable a better prediction of freeze susceptibility. Here, we present a developmental timeline of the preanthesis changes of 'Montmorency' floral buds, ovaries and anthers over 2 years following their completion of chilling and relate these changes to growing degree hours (GDH) and the lethal temperature (LT50) of flowers. Changes in bud dry weight (DW), fresh weight (FW), volume, and external phenology stage including the percentage of green color development of bud scales were predicted by heat accumulation but were not early predictors of the increasing freeze susceptibility of pistils. Between endodormancy and green tip stage, ovary volume increased nearly threefold and relative water content (RWC) increased from ~ 45 to 70% in both years. A linear mixed regression model indicated that RWC and the interaction between RWC and ovary growth were significant predictors of LT50. Importantly, the loss of ~ 20°C of freeze resistance occurred between 45 and 57% RWC and preceded any detectable changes in bud phenology. Microsporogenesis was observed after dormancy release when measurable changes in the ovary and bud RWC had already occurred. A GDH model estimated freeze sensitivity of pistils and explained 93% of the variation in LT50 during preanthesis development. A simple GDH model to predict critical freeze temperature of pistils should aid producers to manage frost protection.

Jujube witches' broom phytoplasma effectors SJP1 and SJP2 induce lateral bud outgrowth by repressing the ZjBRC1-controlled auxin efflux channel.

Comprehensively controlling phytoplasma-associated jujube witches' broom (JWB) disease is extremely challenging for the jujube industry. Although the pathogenesis of phytoplasma disease has been highlighted in many plant species, the release of lateral buds from dormancy under JWB phytoplasma infection has not been characterized in woody perennial jujube. Here, two 16SrV-B group phytoplasma effectors, SJP1 and SJP2, were experimentally determined to induce witches' broom with increased lateral branches. In vivo interaction and subcellular localization analyses showed that both SJP1 and SJP2 were translocated from the cytoplasm to the nucleus to target the CYC/TB1-TCP transcription factor ZjBRC1. The N- and C-terminal coiled-coil domains of SJP1 and SJP2 were required for the TCP-binding ability. ZjBRC1 bound directly to the auxin efflux carrier ZjPIN1c/3 promoters and down-regulated their expression to promote the accumulation of endogenous auxin indole-3-acetic acid in jujube calli. Furthermore, JWB phytoplasma infection suppressed ZjBRC1 accumulation and induced ZjPIN1c/3 expression to stimulate lateral bud outgrowth. Therefore, SJP1 and SJP2 stimulate lateral bud outgrowth, at least partly, by repressing the ZjBRC1-controlled auxin efflux channel in jujube, representing a potential strategy for comprehensive phytoplasma-associated disease control and a resource for gene editing breeding to create new cultivars with varying degrees of shoot branching.

Molecular reprogramming in grapevine woody tissues at bud burst

Perennial woody plants undergo a period of dormancy from the beginning of autumn until the end of spring. Whereas the molecular and physiological events that characterize dormancy release of buds have been described in detail, those occurring in woody tissues underneath the buds are mostly unknown. To bridge this gap, the mRNA populations of cane segments located underneath the bud were analyzed at bud dormancy (E-L 1) and at bud burst (E-L 4). They revealed an important reprogramming of gene expression suggesting that cell division, cell wall metabolism and the mobilization of sugars are the main metabolic and cellular events occurring in cane woody tissues at bud burst. Also, the upregulation of several genes of sugar metabolism, encoding starch- and sucrose-degrading enzymes and sugar transporters, correlates with the decrease in starch and soluble sugars in woody tissues concomitant with increased sucrose synthase and α-amylolytic biochemical activities. The latter is likely due to the VviAMY2 gene that encodes a functional α-amylase as observed after its heterologous expression in yeast. Taken together, these results are consistent with starch and sugar mobilization in canes being primarily involved in grapevine secondary growth initiation and supporting the growth of the emerging bud.

Secondary and tertiary budbreak release is enhanced by extended dormancy chilling in 'Shiraz' grapevines

Limited information exists regarding the dormancy of secondary and tertiary buds within the compound bud of grapevines. We were interested to evaluate how extended chilling duration would affect the budbreak percentage of all three bud orders within the compound bud. Dormant potted 'Shiraz' grapevines, with thirty retained buds per vine, were placed in a cool room at 4 °C over a 20-month period to extend dormancy. Vines were then systematically removed over five dates and placed in a controlled growth environment to assess budbreak percentages and cane tissue concentrations of abscisic acid and cytokinins. Budbreak was hastened by at least 13 d with vines receiving any extra chilling compared to no initial chilling. Furthermore, the firstly observed correlative inhibition of basal buds was apparently removed with chilling. Removal of correlative inhibition within the compound bud with increased chilling duration was also observed with the increases of secondary (doubles) and tertiary (triples) buds breaking simultaneously with the primary bud at each node. This resulted in 91 % of the nodes having two developing shoots and 56 % of the nodes presenting three developing shoots by the end of the experiment. Furthermore, a sigmoidal relationship between percent secondary buds and chilling duration was observed. Possible phytohormone connections were observed with the decline of ABA as secondary and tertiary buds broke at 414 d of chilling and depletion of the CKs, which coincided with the greatest rate of primary bud break after 242 d of chilling. Other possible involvement of ABA and Cis-type cytokinin interactions with secondary and tertiary bud dormancy is discussed. The results suggest future investigations into secondary and tertiary bud release within the grapevine using similar techniques may help to better understand the biochemical mechanisms associated with dormancy.

Identification of early and late flowering time candidate genes in endodormant and ecodormant almond flower buds.

Flower bud dormancy in temperate fruit tree species, such as almond [Prunus dulcis (Mill.) D.A. Webb], is a survival mechanism that ensures that flowering will occur under suitable weather conditions for successful flower development, pollination and fruit set. Dormancy is divided into three sequential phases: paradormancy, endodormancy and ecodormancy. During the winter, buds need cultivar-specific chilling requirements (CRs) to overcome endodormancy and heat requirements to activate the machinery to flower in the ecodormancy phase. One of the main factors that enables the transition from endodormancy to ecodormancy is transcriptome reprogramming. In this work, we therefore monitored three almond cultivars with different CRs and flowering times by RNA sequencing during the endodormancy release of flower buds and validated the data by quantitative real-time PCR in two consecutive seasons. We were thus able to identify early and late flowering time candidate genes in endodormant and ecodormant almond flower buds associated with metabolic switches, transmembrane transport, cell wall remodeling, phytohormone signaling and pollen development. These candidate genes were indeed involved in the overcoming of the endodormancy in almond. This information may be used for the development of dormancy molecular markers, increasing the efficiency of temperate fruit tree breeding programs in a climate-change context.

The influence of autumn-winter temperatures on endodormancy release and blooming performance of apricot (Prunus armeniaca L.) in central Italy based on long-term observations

ABSTRACT In the context of global warming, mild winter temperatures could compromise the fulfilment of the chilling requirement (CR) for overcoming flower bud endodormancy, impacting on the yields of perennial species such as apricot (Prunus armeniaca L.). Long-term and site-specific data on air temperatures allowed us to explore the influence of yearly chill accumulation on the endodormancy release of flower buds and blooming responses of two apricot cultivars (‘San Castrese’ and ‘Orange Red’) selected as models for their different characteristics such as geographical origin, CRs of flower buds, blooming time, and fruiting regularity. The CR for breaking flower bud endodormancy was determined by the ‘forcing test’, and the accumulation of chill temperatures was estimated using the Chilling Units (CUs) model. Since the 1990s, milder autumn–winter temperatures and a decline in CUs were recorded. These occurrences had consequences on the endodormancy release, influencing date, and intensity of blooming. ‘San Castrese’, although able to conform to warmer winters, showed the most significant changes in terms of blooming date delay, and reduction in blooming and fruiting intensity. Based on the irregular winter chilling locally verified over several years, serious alterations in apricot floral biology can be predicted.

Characterizing rhizome bud dormancy in Polygonatum kingianum: Development of novel chill models and determination of dormancy release mechanisms by weighted correlation network analysis.

This study was conducted to explore specific chill models and the mechanisms underlying rhizome bud dormancy break in Polygonatum kingianum. Rhizome buds were subjected to various chilling temperatures for different duration and then transferred to warm conditions for germination and subsequent evaluation of their response to temperature and chilling requirements. A CUkingianum model was constructed to describe the contribution of low temperature to the chill unit, and it was suggested that 2.97°C was the optimum temperature and that 11.54°C was the upper limit for bud release. The CASkingianum model showed the relationship between chilling accumulation and sprouting percentage; therefore, rhizome bud development could be predicted through the model. Weighted correlation network analysis (WGCNA) of transcriptomic data of endo-, eco- and nondormant rhizome buds generated 33 gene modules, 6 of which were significantly related to bud sprouting percentage. In addition, 7 significantly matched transcription factors (TFs) were identified from the promoters of 17 "real" hub genes, and DAG2 was the best matched TF that bound to AAAG element to regulate gene expression. The current study is valuable for developing a highly efficient strategy for seedling cultivation and provides strong candidates for key genes related to rhizome bud dormancy in P. kingianum.

Virulent Rhodococcus fascians Produce Unique Methylated Cytokinins.

Some strains of Rhodococcus fascians exist only as epiphytes on the plant surface whereas others can become endophytic and cause various abnormalities including the release of multiple buds and reduced root growth. The abnormalities reflect the action of cytokinin. The strains that can become endophytic harbour a linear plasmid that carries cytokinin biosynthesis, activation and destruction genes. However, both epiphytic and endophytic forms can release cytokinin into culture, affect cytokinin metabolism within inoculated plants and enhance the expression of sugar and amino acid transporters and cell wall invertases, but only the endophytic form markedly affects the morphology of the plant. A unique methylated cytokinin, dimethylated N6-(∆2-isopentenyl)adenine (2-MeiP), operating in a high sugar environment, is the likely causative factor of the severe morphological abnormalities observed when plants are inoculated with R. fascians strains carrying the linear plasmid.