Application Of Cytokinin Research Articles

Exogenously Applied Gibberellic Acid Alters Cannabinoid Profile in Cannabis sativa L.

Cannabis sativa (C. sativa L.) has garnered significant attention worldwide due to its widespread use as a pharmaceutical agent. With the increasing clinical application of C. sativa and cannabinoid therapeutics, there is strong interest in the development of superior plant varieties and optimisation of growth conditions to enhance secondary metabolite yield. Our RNA sequencing analysis revealed differential expression of hormone-related transcripts in developing C. sativa trichomes, suggesting the involvement of hormone signalling pathways in cannabinoid production. Leveraging the potency of exogenous hormones on plants, this study sought to determine if the application of cytokinin (CK), gibberellic acid (GA) and jasmonic acid (JA) modified trichome morphology and the cannabinoid profile over an 8-week period following the induction of flowering. Exogenous hormone application led to alterations in trichome morphology, with each treatment significantly reducing trichome head width by the final week of assessment. Interestingly, GA application also resulted in a significant reduction in the concentration of Δ-9-tetrahydrocannabinol (THC), Δ-9-tetrahydrocannabinolic acid (THCA), cannabidiol (CBD) and cannabidiolic acid (CBDA) by week 8 post floral induction, however, JA and CK treatment did not consistently modulate the accumulation of these cannabinoids. The minor cannabinoids, cannabidivaranic acid (CBDVA), cannabicyclolic acid (CBLA), cannabicyclol (CBL), cannabichromene (CBC), cannabigerolic acid (CBGA) and cannabigerol (CBG), were also affected by hormone treatments, with varying degrees of accumulation observed. These findings underscore the intricate interplay between phytohormones and secondary metabolite biosynthesis in C. sativa. Our study highlights the potential of hormone modulation as a strategy to enhance cannabinoid yield and offers some insights into the regulatory mechanisms governing cannabinoid biosynthesis in C. sativa trichomes.

The Compact Root Architecture 2 systemic pathway is required for the repression of cytokinins and miR399 accumulation in Medicago truncatula N-limited plants.

Legume plants can acquire mineral nitrogen (N) either through their roots or via a symbiotic interaction with N-fixing rhizobia bacteria housed in root nodules. To identify shoot-to-root systemic signals acting in Medicago truncatula plants at N deficit or N satiety, plants were grown in a split-root experimental design in which either high or low N was provided to half of the root system, allowing the analysis of systemic pathways independently of any local N response. Among the plant hormone families analyzed, the cytokinin trans-zeatin accumulated in plants at N satiety. Cytokinin application by petiole feeding led to inhibition of both root growth and nodulation. In addition, an exhaustive analysis of miRNAs revealed that miR2111 accumulates systemically under N deficit in both shoots and non-treated distant roots, whereas a miRNA related to inorganic phosphate (Pi) acquisition, miR399, accumulates in plants grown under N satiety. These two accumulation patterns are dependent on Compact Root Architecture 2 (CRA2), a receptor required for C-terminally Encoded Peptide (CEP) signaling. Constitutive ectopic expression of miR399 reduced nodule numbers and root biomass depending on Pi availability, suggesting that the miR399-dependent Pi-acquisition regulatory module controlled by N availability affects the development of the whole legume plant root system.

A nitrogen-responsive cytokinin oxidase/dehydrogenase regulates root response to high ammonium in rice.

Plant root system is significantly influenced by high soil levels of ammonium nitrogen, leading to reduced root elongation and enhanced lateral root branching. In Arabidopsis, these processes have been reported to be mediated by phytohormones and their downstream signaling pathways, while the controlling mechanisms remain elusive in crops. Through a transcriptome analysis of roots subjected to high/low ammonium treatments, we identified a cytokinin oxidase/dehydrogenase encoding gene, CKX3, whose expression is induced by high ammonium. Knocking out CKX3 and its homologue CKX8 results in shorter seminal roots, fewer lateral roots, and reduced sensitivity to high ammonium. Endogenous cytokinin levels are elevated by high ammonium or in ckx3 mutants. Cytokinin application results in shorter seminal roots and fewer lateral roots in wild-type, mimicking the root responses of ckx3 mutants to high ammonium. Furthermore, CKX3 is transcriptionally activated by type-B RR25 and RR26, and ckx3 mutants have reduced auxin content and signaling in roots under low ammonium. This study identified RR25/26-CKX3-cytokinin as a signal module that mediates root responses to external ammonium by modulating of auxin signaling in the root meristem and lateral root primordium. This highlights the critical role of cytokinin metabolism in regulating rice root development in response to ammonium.

Deciphering the evolutionary development of the "Chinese lantern" within Solanaceae.

The key genetic variation underlying the evo-devo of ICS in Solanaceae may be further pinpointed using an integrated strategy of forward and reverse genetics studies under the framework of phylogeny. The calyx of Physalis remains persistent throughout fruit development. Post-flowering, the fruiting calyx is inflated rapidly to encapsulate the berry, giving rise to a "Chinese lantern" structure called inflated calyx syndrome (ICS). It is unclear how this novelty arises. Over the past 2decades, the role of MADS-box genes in the evolutionary development (evo-devo) of ICS has mainly been investigated within Solanaceae. In this review, we analyze the main achievements, challenges, and new progress. ICS acts as a source for fruit development, provides a microenvironment to protect fruit development, and assists in long-distance fruit dispersal. ICS is a typical post-floral trait, and the onset of its development is triggered by specific developmental signals that coincide with fertilization. These signals can be replaced by exogenous gibberellin and cytokinin application. MPF2-like heterotopic expression and MBP21-like loss have been proposed to be two essential evolutionary events for ICS origin, and manipulating the related MADS-box genes has been shown to affect the ICS size, sepal organ identity, and/or male fertility, but not completely disrupt ICS. Therefore, the core genes or key links in the ICS biosynthesis pathways may have undergone secondary mutations during evolution, or they have not yet been pinpointed. Recently, we have made some encouraging progress in acquiring lantern mutants in Physalis floridana. In addition to technological innovation, we propose an integrated strategy to further analyze the evo-devo mechanisms of ICS in Solanaceae using forward and reverse genetics studies under the framework of phylogeny.

Tea (Camellia sinensis L. O. Kuntze) callus development based on morphological and phytochemical traits applied by variations in plant growth regulators (PGRs)

A variation of the clonal propagation system for tea has been established through in vitro methods, utilizing shoots and leaves derived from primary explants of mature field-grown plants. The research aimed to assess the diversity of tea calluses based on morphological and phytochemical traits derived from leaf and shoot explants on MS media induced by the application of plant growth regulators, including auxin and cytokinin. The research was conducted at the Seed Technology Unit Tissue Culture Laboratory, Faculty of Agriculture, Jatinangor, from April 2022 to February 2023. The experiment employed MS-modified multiplication media and PGR, with BAP at 9 mg/L, TDZ at 1.0 mg/L, Zeatin at 0.1 mg/L, NAA at 0.01 mg/L, and 1 mg/L. Results indicated that applying PGR, auxin, and cytokinin with MS media influenced morphological and phytochemical traits of tea's callus derived from leaves and shoots. Specifically, the treatment of 1 mg/L NAA + 1 mg/L BAP showed the best performance on callus weight and total phenolic and flavonoid contents compared to other treatments., i.e. 9.038% % and 0.05% %, respectively. The success of clonal propagation in tea through in vitro methods is expected to increase by carefully selecting the appropriate source and type of explant, planting media, PGR, and addressing potential contaminants.

Transcriptomic and Physiological Analyses for the Role of Hormones and Sugar in Axillary Bud Development of Wild Strawberry Stolon.

Strawberries are mainly propagated by stolons, which can be divided into monopodial and sympodial types. Monopodial stolons consistently produce ramets at each node following the initial single dormant bud, whereas sympodial stolons develop a dormant bud before each ramet. Sympodial stolon encompasses both dormant buds and ramet buds, making it suitable for studying the formation mechanism of different stolon types. In this study, we utilized sympodial stolons from Fragaria nilgerrensis as materials and explored the mechanisms underlying sympodial stolon development through transcriptomic and phytohormonal analyses. The transcriptome results unveiled that auxin, cytokinin, and sugars likely act as main regulators. Endogenous hormone analysis revealed that the inactivation of auxin could influence bud dormancy. Exogenous cytokinin application primarily induced dormant buds to develop into secondary stolons, with the proportion of ramet formation being very low, less than 10%. Furthermore, weighted gene co-expression network analysis identified key genes involved in ramet formation, including auxin transport and response genes, the cytokinin activation gene LOG1, and glucose transport genes SWEET1 and SFP2. Consistently, in vitro cultivation experiments confirmed that glucose enhances the transition of dormant buds into ramets within two days. Collectively, cytokinin and glucose act as dormant breakers, with cytokinin mainly driving secondary stolon formation and glucose promoting ramet generation. This study improved our understanding of stolon patterning and bud development in the sympodial stolon of strawberries.

Efek Pengaplikasian Sitokinin Dan Paclobutrazol Terhadap Ukuran Rimpang Tanaman Kunyit (Curcuma Domestica Val.)

Since COVID-19, the demand for turmeric has continued to increase both domestically and for export opportunities. This encourages the continued development of turmeric cultivation. The use of growth regulators can be done to regulate plant growth patterns. This study aims to determine the effect of the application of cytokinin and paclobutrazole on the size of the rhizomes of turmeric plants (Curcuma domestica Val.). This study used a Randomized Group Design (RAK) with 2 treatment factors, which are : Factor I Cytokinin (S) consists of 3 kinds, namely S1: 0 mg/l water, S2: 10 mg/l water and S3: 20 mg/l water while, Factor II: Paclobutrazole (K) consists of 4 kinds, namely: P1: 0 g/l water, P2: 0.50 g/l water, P3: 0.75 g/l water, P4: 1 g/l water. Based on the results of the experiment, it shows that the application of ZPT Cytokinin (BAP) and Paclobutrazole on turmeric plants gives a real interaction effect on the observation of vegetative growth of plant height, while on the harvest observation variable only gives a real interaction effect on the observation of plant biomass and not real on the number of tubers and tuber weight. The concentration and time of application of cytokinin (BAP) and paclobutrazole will affect the nature of stimulation and inhibition of growth, the application of BAP at a concentration of 10-20 mg / l water can increase growth but if combined with paclobutrazole above 0.75 g / l water will actually have an inhibiting effect.

OsNAC121 regulates root development, tillering, panicle morphology, and grain filling in rice plant.

Transcription factors in coordination with phytohormones form an intricate regulatory network modulating vital cellular mechanisms like development, growth and senescence in plants. In this study, we have functionally characterized the transcription factor OsNAC121 by developing gene silencing and overexpressing transgenic rice plants, followed by detailed analyses of the plant architecture. Transgenic lines exhibited remodelling in crown root development, lateral root structure and density, tiller height and number, panicle and grain morphologies, underpinning the imbalanced auxin: cytokinin ratio due to perturbed auxin transportation. Application of cytokinin, auxin and abscisic acid increased OsNAC121 gene expression nearly 17-, 6- and 91-folds, respectively. qRT-PCR results showed differential expressions of auxin and cytokinin pathway genes, implying their altered levels. A 47-fold higher expression level of OsNAC121 during milky stage in untransformed rice, compared to 14-day old shoot tissue, suggests its crucial role in grain filling; as evidenced by a large number of undeveloped grains produced by the gene silenced lines. Crippled gravitropic response by the transgenic plants indicates their impaired auxin transport. Bioinformatics revealed that OsNAC121 interacts with co-repressor (TOPLESS) proteins and forms a part of the inhibitor complex OsIAA10, an essential core component of auxin signalling pathway. Therefore, OsNAC121 emerges as an important regulator of various aspects of plant architecture through modulation of crosstalk between auxin and cytokinin, altering their concentration gradient in the meristematic zones, and consequently modifying different plant organogenesis processes.

Synergetic light and cytokinin treatments mitigate the recombinant protein yield depression induced by high-density cultivation of hydroponically-grown Nicotiana benthamiana.

Plant molecular farming is currently operating a transition from soil-based cultures towardhydroponic systems. In this study, we designed a whole-plant NFT (nutrient film technique) platform for the transient expression of influenza virus-like particles harboring hemagglutinin H1 proteins in Nicotiana benthamiana. In particular, we examined the effects of plant density during the post-infiltration expression phase on plant growth and H1 yield in relation to the daily light integral (DLI) received by the crop and the exogenous application of 6-BAP cytokinin (CK). We expected from previous work that high DLI and CK treatments would stimulate the development of highly productive leaves on axillary (secondary) stems and thereby improve the H1 yield at the whole-plant scale. Increasing plant density from 35.7 to 61 plants m-2 during the post-infiltration phase significantly decreased the proportion of axillary leaf biomass by 30% and H1 yield per plant by 39%, resulting in no additional yield gain on a whole-crop area basis. Adding CK to the recirculated nutrient solution decreased the harvested leaf biomass by 31% and did not enhance the relative proportion of S leaves of the plants as previously reported with foliar CK application. There was a 36% increase in H1 yield when doubling the DLI from 14 to 28 mol m-2 s-1, and up to 71% yield gain when combining such an increase in DLI with the hydroponic CK treatment. Contrary to our expectations, leaves located on the main stem, particularly those from the upper half of the plant (i.e.,eighth leaf and above), contributed about 80% of total H1 yield. Our study highlights the significantly different phenotype (~30% less secondary leaf biomass) and divergent responses to light and CK treatments of NFT-grown N. benthamiana plants compared to previous studies conducted on potted plants.

The Application Timing of a Cytokinin B-Mo-based Product Affects the Characteristics of Rooted Cuttings and Nonstructural Carbohydrates of Coleus (Plectranthus scutellarioides cv. Wild Lime) during Adventitious Root Development

A large group of horticulture species are propagated vegetatively through shoot-tip cuttings harvested from stock plants and planted to form adventitious roots. Adventitious rooting leads to establishing a carbohydrate sink in the region of root regeneration that is highly dependent on energy and carbon skeletons. We hypothesized that the timing of exogenous applications of cytokinin (CK) and boron (B)–molybdenum (Mo)-based products during adventitious root development can affect the flow of sugars from leaves to sinks, carbon allocation to the adventitious roots, and the quality of rooted cuttings. During this project, we aimed to determine if the application time of a CK/B-Mo-based product during the adventitious root development of unrooted cuttings would impact the source-to-sink relationship and, hence, affect plug growth and quality. A sink-strengthening commercial product based on cytokinin, B, and Mo was applied at four plug development stages plus a negative control as follows: T1, plants without product (control); T2, sticking stage (starting 24 hours after the sticking); T3, callus formation stage; T4, root development stage; and T5, toning stage. The root and shoot lengths and dry matter, number of leaves, leaf chlorophyll content, root-to-shoot ratio (based on dry matter), and nonstructural carbohydrate contents were measured. The timing of the application of the product impacted the root development, quality of the cuttings, and nonstructural carbohydrate content. Product application during the adventitious root dedifferentiation and induction phases (T2) resulted in the shortest root and shoot lengths, lowest dry matter accumulation, lowest nonstructural carbohydrate contents, and some phytotoxicity. Application during the initiation phase (T3) resulted in greater root length, total dry matter, and total soluble sugar contents compared with the control. Application during the expression phase (T4) resulted in the largest root length and mass and the highest sucrose contents. Applying the product when the roots had grown and reached all the edges of the growing media (T5) did not have any benefits compared with the control. This study provides new insights into the application timing of exogenous CKs, B, and Mo to generate a well-toned rooted coleus cutting and potential explanations in relation to nonstructural carbohydrate metabolism.

Induced Water Deficit Tolerance in Hexaploid Wheat through Exogenous Application of Trehalose and Cytokinins: Water Relations and Physiological Changes

Induced Water Deficit Tolerance in Hexaploid Wheat through Exogenous Application of Trehalose and Cytokinins: Water Relations and Physiological Changes

Rice bundle sheath cell shape is regulated by the timing of light exposure during leaf development.

Plant leaves contain multiple cell types which achieve distinct characteristics whilst still coordinating development within the leaf. The bundle sheath possesses larger individual cells and lower chloroplast content than the adjacent mesophyll, but how this morphology is achieved remains unknown. To identify regulatory mechanisms determining bundle sheath cell morphology we tested the effects of perturbing environmental (light) and endogenous signals (hormones) during leaf development of Oryza sativa (rice). Total chloroplast area in bundle sheath cells was found to increase with cell size as in the mesophyll but did not maintain a 'set-point' relationship, with the longest bundle sheath cells demonstrating the lowest chloroplast content. Application of exogenous cytokinin and gibberellin significantly altered the relationship between cell size and chloroplast biosynthesis in the bundle sheath, increasing chloroplast content of the longest cells. Delayed exposure to light reduced the mean length of bundle sheath cells but increased corresponding leaf length, whereas premature light reduced final leaf length but did not affect bundle sheath cells. This suggests that the plant hormones cytokinin and gibberellin are regulators of the bundle sheath cell-chloroplast relationship and that final bundle sheath length may potentially be affected by light-mediated control of exit from the cell cycle.

Transcription factor FveMYB117a inhibits axillary bud outgrowth by regulating cytokinin homeostasis in woodland strawberry.

Shoot branching affects plant architecture. In strawberry (Fragaria L.), short branches (crowns) develop from dormant axillary buds to form inflorescences and flowers. While this developmental transition contributes greatly to perenniality and yield in strawberry, its regulatory mechanism remains unclear and understudied. In the woodland strawberry (Fragaria vesca), we identified and characterized 2 independent mutants showing more crowns. Both mutant alleles reside in FveMYB117a, a R2R3-MYB transcription factor gene highly expressed in shoot apical meristems, axillary buds, and young leaves. Transcriptome analysis revealed that the expression of several cytokinin pathway genes was altered in the fvemyb117a mutant. Consistently, active cytokinins were significantly increased in the axillary buds of the fvemyb117a mutant. Exogenous application of cytokinin enhanced crown outgrowth in the wild type, whereas the cytokinin inhibitors suppressed crown outgrowth in the fvemyb117a mutant. FveMYB117a binds directly to the promoters of the cytokinin homeostasis genes FveIPT2 encoding an isopentenyltransferase and FveCKX1 encoding a cytokinin oxidase to regulate their expression. Conversely, the type-B Arabidopsis response regulators FveARR1 and FveARR2b can directly inhibit the expression of FveMYB117a, indicative of a negative feedback regulation. In conclusion, we identified FveMYB117a as a key repressor of crown outgrowth by inhibiting cytokinin accumulation and provide a mechanistic basis for bud fate transition in an herbaceous perennial plant.

OsRR26, a type-B response regulator, modulates salinity tolerance in rice via phytohormone-mediated ROS accumulation in roots and influencing reproductive development.

OsRR26 is a cytokinin-responsive response regulator that promotes phytohormone-mediated ROS accumulation in rice roots, regulates seedling growth, spikelet fertility, awn development, represses NADPH oxidases, and negatively affects salinity tolerance. Plant two-component systems (TCS) play a pivotal role in phytohormone signaling, stress responses, and circadian rhythm. However, a significant knowledge gap exists regarding TCS in rice. In this study, we utilized a functional genomics approach to elucidate the role of OsRR26, a type-B response regulator in rice. Our results demonstrate that OsRR26 is responsive to cytokinin, ABA, and salinity stress, serving as the ortholog of Arabidopsis ARR11. OsRR26 primarily localizes to the nucleus and plays a crucial role in seedling growth, spikelet fertility, and the suppression of awn development. Exogenous application of cytokinin led to distinct patterns of reactive oxygen species (ROS) accumulation in the roots of both WT and transgenic plants (OsRR26OE and OsRR26KD), indicating the potential involvement of OsRR26 in cytokinin-mediated ROS signaling in roots. The application of exogenous ABA resulted in varied cellular compartmentalization of ROS between the WT and transgenic lines. Stress tolerance assays of these plants revealed that OsRR26 functions as a negative regulator of salinity stress tolerance across different developmental stages in rice. Physiological and biochemical analyses unveiled that the knockdown of OsRR26 enhances salinity tolerance, characterized by improved chlorophyll retention and the accumulation of soluble sugars, K+ content, and amino acids, particularly proline.

Response of Bread Wheat Cultivars to Terminal Water Stress and Cytokinin Application from a Grain Phenotyping Perspective

A better understanding of the responsiveness of grain phenotypic indices to terminal water stress (TWS) in wheat might help explain grain weight variations and determine which grain traits are most affected. A two-year field experiment (2020–2021 and 2021–2022) was conducted to identify how TWS and exogenous cytokinin application might affect grain weight and grain dimensions in three bread wheat cultivars using high-throughput digital image phenotyping. The results showed that the effects of growing seasons, irrigation, and cultivars were significant on grain weight and phenotypic indices. In our study, TWS significantly reduced thousand grain weight (24.62%, 14.65%) and grain development in the width directions MinFeret, i.e., minimum caliper diameter (10.70%, 6.64%) and Minor, i.e., the minor axes of the best fitted ellipses to the grains (10.91%, 6.65%), or synthesized indices including Area/Perim. (9.01%, 5.42%), Area × Circ. (17.30%, 10.13%), Minor/Solid. (10.26%, 6.32%), MinFeret/Solid. (10.01%, 6.11%), Area × Solid (13.94%, 7.96%), Perim. × Circ. (9.07%, 5.42%), A1 (29.99%, 17.09%), and A2 (30.20%, 17.27%) in each growing season, respectively. Regardless of the factors causing these variations, a sustained relationship was found between thousand grain weight and phenotypic indices, with significant positive correlations. The stronger positive correlation between thousand grain weight and grain width indices (r ≥ 0.965) showed important implications for grain development and filling. The Torabi cultivar performed better than the Sirvan and Pishgam in both growing season conditions. In addition, the technical advantages of developing phenotyping approaches, the present study could contribute to a better physiological evaluation of wheat cultivars in multivariate environments.

Alterações morfológicas e bioquímicas em abóbora com frutificação induzida por citocinina e auxina

ABSTRACT The use growth regulators from the cytokinins and auxins group has been shown to increase the productivity of certain crops, as they may be involved in the expression of plant sex, although little is known about the action of auxin IBA and cytokinin CPPU on the fruiting of squash, as well as the interaction between both, which makes this field of study promising. Thus, the objective of this study was to induce the fruiting in Atlas squash, by means of different forms of application and proportions of cytokinin and auxin and to evaluate their effects on the physical-chemical characteristics of the fruits. The treatments were composed of six proportions associated with growth regulators and of two forms of application. The experimental design was a randomized block design with four replicates. At 72 days after transplanting, growth and fruit quality analyses were performed. The behavior of the hormones is modulated by their concentration and place of application, and the effect may be beneficial or not. The proportions 50/50% via leaf and 75/25% via ovary were the ones that increased the growth and parameters of fruit quality. The application of CPPU via leaf at higher concentration in proportion decreases quality characteristics such as vitamin C, carotenoids and starch.

Cytokinin and indole-3-acetic acid crosstalk is indispensable for silicon mediated chromium stress tolerance in roots of wheat seedlings

The rising heavy metal contamination of soils imposes toxic impacts on plants as well as other life forms. One such highly toxic and carcinogenic heavy metal is hexavalent chromium [Cr(VI)] that has been reported to prominently retard the plant growth. The present study investigated the potential of silicon (Si, 10 µM) to alleviate the toxicity of Cr(VI) (25 µM) on roots of wheat (Triticum aestivum L.) seedlings. Application of Si to Cr(VI)-stressed wheat seedlings improved their overall growth parameters. This study also reveals the involvement of two phytohormones, namely auxin and cytokinin and their crosstalk in Si-mediated mitigation of the toxic impacts of Cr(VI) in wheat seedlings. The application of cytokinin alone to wheat seedlings under Cr(VI) stress reduced the intensity of toxic effects of Cr(VI). In combination with Si, cytokinin application to Cr(VI)-stressed wheat seedlings significantly minimized the decrease induced by Cr(VI) in different parameters such as root-shoot length (10.8% and 13%, respectively), root-shoot fresh mass (11.3% and 10.1%, respectively), and total chlorophyll and carotenoids content (13.4% and 6.8%, respectively) with respect to the control. This treatment also maintained the regulation of proline metabolism (proline content, and P5CS and PDH activities), ascorbate-glutathione (AsA-GSH) cycle and nutrient homeostasis. The protective effect of Si and cytokinin against Cr(VI) stress was minimized upon supplementation of an inhibitor of polar auxin transport- 2,3,5-triiodobenzoic acid (TIBA) which suggested a potential involvement of auxin in Si and cytokinin-mediated mitigation of Cr(VI) toxicity. The exogenous addition of a natural auxin – indole-3-acetic acid (IAA) confirmed auxin is an active member of a signaling cascade along with cytokinin that aids in Si-mediated Cr(VI) toxicity alleviation as IAA application reversed the negative impacts of TIBA on wheat roots treated with Cr(VI), cytokinin and Si. The results of this research are also confirmed by the gene expression analysis conducted for nutrient transporters (Lsi1, CCaMK, MHX, SULT1 and ZIP1) and enzymes involved in the AsA-GSH cycle (APX, GR, DHAR and MDHAR). The overall results of this research indicate towards possible induction of a crosstalk between cytokinin and IAA upon Si supplementation which in turn stimulates physiological, biochemical and molecular changes to exhibit protective effects against Cr(VI) stress. Further, the information obtained suggests probable employment of Si, cytokinin and IAA alone or combined in agriculture to maintain plant productivity under Cr(VI) stress and data regarding expression of key genes can be used to develop new crop varieties with enhanced resistance against Cr(VI) stress together with its reduced load in seedlings.

Micropropagation of Lisianthus [Eustoma grandiflorum (Raf.) Shinn.] Leaf Explants and Single Nodes in Response to Plant Growth Regulators

Lisianthus has long-lasting, white, blue-purple, velvet or pink flowers. Varieties that can be used in pots, outdoors, or cut flowers are widely used and it is essential to develop new varieties to increase their commercial value. Breeding studies with classical methods can take a long time in lisianthus. Techniques to create variation in these plants and facilitate their reproduction always contribute to shortening the breeding period and one of the best known of these methods is plant tissue culture. This study aimed to investigate the micropropagation possibilities in lisianthus and examine the effects of auxin and cytokinin applications and doses on shoot reproduction. Supplemented with 10 different plant growth regulators in Murashige and Skoog (MS) medium, leaf explants from lisianthus plants that were germinated under in vitro conditions (seedlings) were cultivated. 6-benzyl aminopurine (BAP) was utilized in 5 doses (0.5, 1.0, 2.0, 3.0, and 4.0 mg L-1) alone in the first 5 groups. Naphthalene acetic acid (NAA) was also added to the BAP mediums at a concentration of 0.5 mg L-1. Shoot formation, shoot lengths, the number of shoots longer and shorter than 1 cm, and regeneration of new shoots after subcultures were determined. According to the results, MS mediums containing 3.0 and 4.0 mg L-1 BAP could be good starting mediums for regenerating new lisianthus shoots from leaf explants. These treatments got the highest values both in shoot formation and the number of shoots longer than 1 cm. It has been determined that 3.0 mg L-1 BAP alone can be used for both organogenesis from leaf explants and shoot proliferation in single node culture. In vitro shoots of the lisianthus species were easily rooted and both PGR-free MS or ½ MS mediums. Lisianthus shoots propagated under in vitro conditions can be rooted under ex vitro conditions both in the float hydroculture and in the soil mixture. The acclimatization stage was optimized also successfully.

Petal size is controlled by the MYB73/TPL/HDA19-miR159-CKX6 module regulating cytokinin catabolism in Rosa hybrida

The size of plant lateral organs is determined by well-coordinated cell proliferation and cell expansion. Here, we report that miR159, an evolutionarily conserved microRNA, plays an essential role in regulating cell division in rose (Rosa hybrida) petals by modulating cytokinin catabolism. We uncover that Cytokinin Oxidase/Dehydrogenase6 (CKX6) is a target of miR159 in petals. Knocking down miR159 levels results in the accumulation of CKX6 transcripts and earlier cytokinin clearance, leading to a shortened cell division period and smaller petals. Conversely, knocking down CKX6 causes cytokinin accumulation and a prolonged developmental cell division period, mimicking the effects of exogenous cytokinin application. MYB73, a R2R3-type MYB transcription repressor, recruits a co-repressor (TOPLESS) and a histone deacetylase (HDA19) to form a suppression complex, which regulates MIR159 expression by modulating histone H3 lysine 9 acetylation levels at the MIR159 promoter. Our work sheds light on mechanisms for ensuring the correct timing of the exit from the cell division phase and thus organ size regulation by controlling cytokinin catabolism.

USE OF CYTOKININS AND COMPOSTING TO IMPROVE THE AGRONOMIC AND PHYSIOLOGICAL TRAITS OF CAIGUA (CYCLANTHERA PEDATA L.)

The scarcity of nutrients and synthetic fertilizers reduced crop productivity, increasing production costs and prompting scientists to seek new technologies to ensure high-quality output. In this context, using cytokinins with organic fertilizers ensued to assess their effects on caigua (Cyclanthera pedata L.) production. For this purpose, land preparation for planting comprised two levels of cytokinins (100 and 150 ml, Anthesis Plus per 200 L of water) and organic compost at 10 t/ha, then spread across the land. Results showed that adding cytokinins and compost manure, alone and in combination, significantly improved the agronomic and physiological characteristics of caigua. However, the combined application of compost manure and cytokinins dramatically enriched the caigua plant length, diameter, fruits per plant, and fruit dry and fresh weight per plant up to 85.0%, 46.9%, 81.8%, 80.6%, and 83.2%, respectively, in comparison with the control treatment. Similarly, chlorophyll contents, quantum yield, photosynthetically active radiation, fluorescence yield, and electron transport reaction increased at 68.8%, 66.4%, 79.2%, 51.1%, and 74.0%, respectively, with combined application as compared with control. Furthermore, the co-addition of composting and cytokinins also upgraded the biochemical composition versus the control. The presented results suggested that applying a mixture of compost manure and cytokinins may help enhance caigua plant growth, yield, and quality and improve soil characteristics.