Cotyledon Development Research Articles

Roles of Germin-like Protein Family in Response to Seed Germination and Shoot Branching in Brassica napus

Germin-like proteins (GLPs) play important roles in the regulation of various plant development processes, such as seed vigor, root and leaf development and disease resistance, while the roles of GLPs on agronomic traits are rarely studied in Brassica napus. Here, we identified GLPs family genes in rapeseed and analyzed their potential functions. There are 77 GLPs family genes (BnGLPs) in the Zhongshuang11 rapeseed reference genome, divided into a, b, c, d, e, f six subfamilies. Tissue expression profile analysis of BnGLPs revealed the following: e subfamily genes were highly expressed in early stages of silique, cotyledon, vegetative rosette and leaf development; f subfamily genes were highly expressed in seed development; genes of a subfamily were mainly expressed in the root; and genes of b, c, d subfamily exhibited low-level or no expression in above mentioned tissues. RT-qPCR analysis confirmed that the transcripts of two f subfamily members decreased dramatically during seed germination, suggesting that f subfamily proteins may play vital roles in the early stage of seed germination. Transcriptome analysis of axillary buds in sequential developing stages revealed that the transcripts of eight e subfamily genes showed a rapid increase at the beginning of shoot branching, implying that the e subfamily members played vital roles in branch development. These results demonstrate that rapeseed BnGLPs likely play essential roles in seedling development, root development and plant architecture, indicating that harnessing certain BnGLPs may contribute to the improvement of rapeseed yield.

A Soybean Pyrroline-5-Carboxylate Dehydrogenase GmP5CDH1 Modulates Plant Growth and Proline Sensitivity

Soybean [Glycine max (L.) Merr.], as a globally commercialized crop, is an important source of protein and oil for both humans and livestock. With more frequent extreme weather disasters, abiotic stress has become one of the critical factors restricting soybean production. Proline (Pro) is a well-known substance in plants that responds to abiotic stress. To identify potential effector genes involved in soybean resistance to abiotic stress, we focused on the pyrroline-5-carboxylate dehydrogenase (P5CDH) which is a key enzyme in the degradation process of Pro. Through homologous sequence alignment, phylogenetic tree, and predicted expression, we chose GmP5CDH1 (Glyma.05G029200) for further research. Tissue-specific expression assay showed that GmP5CDH1 had higher expression levels in soybean seed and cotyledon development. Subcellular localization assay revealed that GmP5CDH1 was a nuclear-membrane-localized protein. As the result of the predicted cis-acting regulatory element indicates, the expression level of GmP5CDH1 was induced by low temperature, drought, salt stress, and ABA in soybean. Next, we constructed transgenic Arabidopsis overexpressing GmP5CDH1. The results showed that GmP5CDH1 also strongly responded to exogenous Pro, and overcame the toxicity of abiotic stress on plants by regulating the endogenous concentration of Pro. The interaction between GmP5CDH1 and GmSAM1 was validated through yeast two-hybrid, LUC fluorescence complementary, and BIFC. In conclusion, overexpression of a soybean pyrroline-5-carboxylate dehydrogenase GmP5CDH1 regulates the development of Arabidopsis thaliana by altering proline content dynamically under salt stress, especially improving the growth of plants under exogenous Pro.

ALOG/LSHs, a novel class of transcription factors: Evolutionarily conserved regulators of plant growth and development.

The ALOG/LSH group of proteins is highly conserved across plant lineage, starting from moss to higher flowering plants, suggesting their crucial role in the evolution and adaptation of land plants. The role of ALOG proteins is highly conserved in various developmental responses, such as vegetative and reproductive developmental programs. Their role in meristem identity, cotyledon development, seedling photomorphogenesis and leaf and shoot development has been relatively well established. Moreover, several key pieces of evidence suggest their role in inflorescence architecture and flower development, including male and female reproductive organs and flower colouration. Recent research has started to explore their role in stress response. Functionally, ALOG proteins have been demonstrated to act as transcriptional regulators and are considered a newly emerging class of transcription factors in plants that regulate diverse developmental and physiological processes. This review aims to stimulate discussion about their role in plant development and their role as transcription factors. It also aims to further unravel the underlying molecular mechanism by which they regulate growth and development throughout the plant lineage.

Peanut LEAFY COTYLEDON1-type genes participate in regulating the embryo development and the accumulation of storage lipids.

Two peanut LEC1-type genes exhibit partial functional redundancy. AhNFYB10 could complement almost all the defective phenotypes of lec1-2 in terms of embryonic morphology, while AhNF-YB1 could partially affect these phenotypes. LEAFY COTYLEDON1 (LEC1) is a member of the nuclear factor Y (NF-Y) family of transcription factors and has been identified as a key regulator of embryonic development. In the present study, two LEC1-type genes from Arachis hypogeae were identified and designated as AhNF-YB1 and AhNF-YB10; these genes belong to subgenome A and subgenome B, respectively. The functions of AhNF-YB1 and AhNF-YB10 were investigated by complementation analysis of their defective phenotypes of the Arabidopsis lec1-2 mutant and by ectopic expression in wild-type Arabidopsis. The results indicated that both AhNF-YB1 and AhNF-YB10 participate in regulating embryogenesis, embryo development, and reserve deposition in cotyledons and that they have partial functional redundancy. In contrast, AhNF-YB10 complemented almost all the defective phenotypes of lec1-2 in terms of embryonic morphology and hypocotyl length, while AhNF-YB1 had only a partial effect. In addition, 30-40% of the seeds of the AhNF-YB1 transformants exhibited a decreasing germination ratio and longevity. Therefore, appropriate spatiotemporal expression of these genes is necessary for embryo morphogenesis at the early development stage and is responsible for seed maturation at the mid-late development stage. On the other hand, overexpression of AhNF-YB1 or AhNF-YB10 at the middle to late stages of Arabidopsis seed development improved the weight, oil content, and fatty acid composition of the transgenic seeds. Moreover, the expression levels of several genes associated with fatty acid synthesis and embryogenesis were significantly greater in developing AhNF-YB10-overexpressing seeds than in control seeds. This study provides a theoretical basis for breeding oilseed crops with high yields and high oil content.

Polycotyly: How Little Do We Know?

Polycotyly, an interesting characteristic of seed-bearing dicotyledonous plants with more than two cotyledons, represents one of the least explored plant characters for utilization, even though cotyledon number was used to classify flowering plants in 1682. Gymnosperm and angiosperm species are generally known to have one or two cotyledons, but scattered reports exist on irregular cotyledon numbers in many plant species, and little is known about the extent of polycotyly in plant taxa. Here, we attempt to update the documentation of reports on polycotyly in plant species and highlight some lines of research for a better understanding of polycotyly. This effort revealed 342 angiosperm species of 237 genera in 80 (out of 416) families and 160 gymnosperm species of 26 genera in 6 (out of 12) families with reported or cited polycotyly. The most advanced research included the molecular-based inference of the phylogeny of flowering plants, showing a significant departure from the cotyledon-based classification of angiosperm plants, and the application of genetic cotyledon mutants as tools to clone and characterize the genes regulating cotyledon development. However, there were no reports on breeding lines with a 100% frequency of polycotyly. Research is needed to discover plant species with polycotyly and to explore the nature, development, genetics, evolution, and potential use of polycotyly.

Onion cryptochrome 1 (AcCRY1) regulates photomorphogenesis and photoperiod flowering in Arabidopsis and exploration of its functional mechanisms under blue light

Cryptochromes (CRYs), as blue-light photoreceptors, play a crucial role in regulating flowering time and hypocotyl and cotyledon development. Their physiological functions have been extensively studied in various plant species. However, research on onions remains limited. In this study, we identified AcCRY1 and conducted preliminary investigations into its function. Our results demonstrate that AcCRY1 possesses a conserved domain typical of cryptochromes with high homology to those found in monocots. Furthermore, we examined the expression level of AcCRY1 in onion. The green tissues is significantly higher compared to non-green tissues, and it exhibits a significant response to blue-light induction. AcCRY1 demonstrates cytoplasmic localization under blue-light conditions, while it localizes in the nucleus during darkness, indicating a strong dependence on blue-light for its subcellular distribution. In comparison to cry1, overexpression of AcCRY1 leads to a significant shorten in seedling hypocotyl length, notable expansion of cotyledons, and acceleration of flowering time. The yeast two-hybrid experiment demonstrated the in vitro interaction between AcCRY1, AcCOP1, and AcSPA1. Additionally, BIFC analysis confirmed their interaction in Onion epidermis. Notably, under blue-light conditions, a significantly enhanced binding activity was observed compared to dark conditions. These findings establish a functional foundation for the regulatory role of AcCRY1 in important physiological processes of onion and provide initial insights into the underlying molecular mechanisms.

290 Ewe Undernutrition Alters Cotyledon Development and Function

Abstract Undernutrition is common for animals maintained in a range setting, particularly during periods of drought, and during gestation can be detrimental to offspring development. The placenta is a known mediator for maternal-fetal nutrient exchange, and developmental impacts to the placenta during times of nutritional stress contribute to poor offspring outcomes. The objective of this study was to determine the impacts of maternal nutrient restriction on the development and function of placental cotyledons. Targhee ewes were allocated into two dietary treatment groups for the entirety of gestation. The control group (CON; n = 10) was fed to meet 100% of NRC requirements and the nutrient restricted group (NR; n = 11) was fed to meet 60% of NRC requirements, to mimic the nutritional stress experienced by range ewes during drought. At the time of lambing total placental weight, total cotyledon number, and lamb birth weight were recorded. Cotyledons (n = 3 / placenta) were removed from multiple locations, weighed, and processed for RNA-sequencing. Total placental weight, total cotyledon number, and lamb birth weight were not affected by maternal diet restriction (P > 0.05). Average cotyledon weight was greater in the CON group compared with the NR group (P < 0.05). Gene ontology (GO) and Kyoto encyclopedia of genes and genomes pathways (KEGG) analyses were performed to identify biological pathways involved in placental function and nutrient transfer. Cotyledons from NR singletons vs CON singletons expressed 470 differentially expressed genes (DEGs; P < 0.05; 187 up-regulated, 283 down-regulated). Gene ontology terms represented by DEGs include hormone activity (P = 0.0003) and antigen processing and presentation (P = 0.0004). KEGG pathways of interest include pyruvate metabolism, estrogen signaling, extracellular matrix receptor interaction, and antigen processing and presentation. There were also 426 DEGs (P < 0.05; 195 up-regulated, 231 down-regulated) in cotyledons of NR twins vs CON twins. Represented GO categories include heme binding (P = 0.003) and oxidoreductase activity (P = 0.03). These data show that prolonged nutrient restriction alters cotyledon development and gene expression indicating modifications in placental function. These changes in placental function likely mediate poor offspring developmental outcomes observed following gestational under nutrition.

Vacuolar Sugar Transporter TMT2 Plays Crucial Roles in Germination and Seedling Development in Arabidopsis

Vacuolar sugar transporters transport sugar across the tonoplast, are major players in maintaining sugar homeostasis, and therefore play vital roles in plant growth, development, and biomass yield. In this study, we analyzed the physiological roles of the tonoplast monosaccharide transporter 2 (TMT2) in Arabidopsis. In contrast to the wild type (WT) that produced uniform seedlings, the tmt2 mutant produced three types of offspring: un-germinated seeds (UnG), seedlings that cannot form true leaves (tmt2-S), and seedlings that develop normally (tmt2-L). Sucrose, glucose, and fructose can substantially, but not completely, rescue the abnormal phenotypes of the tmt2 mutant. Abnormal cotyledon development, arrested true leaf development, and abnormal development of shoot apical meristem (SAM) were observed in tmt2-S seedlings. Cotyledons from the WT and tmt2-L seedlings restored the growth of tmt2-S seedlings through micrografting. Moreover, exogenous sugar sustained normal growth of tmt2-S seedlings with cotyledon removed. Finally, we found that the TMT2 deficiency resulted in growth defects, most likely via changing auxin signaling, target of rapamycin (TOR) pathways, and cellular nutrients. This study unveiled the essential functions of TMT2 for seed germination and initial seedling development, ensuring cotyledon function and mobilizing sugars from cotyledons to seedlings. It also expanded the current knowledge on sugar metabolism and signaling. These findings have fundamental implications for enhancing plant biomass production or seed yield in future agriculture.

What is the appropriate content of [formula omitted] irrigated into tomato cultivation soil for enhancing its carbon fixation?

To improve the carbon fixation capacity of crops, HCO3− is applied to the rhizosphere under a suitable pH value, which can enhance the utilization of CO2 by crops. This study aimed to clarify the maximum fixation capacity of HCO3− in tomato plants by exploring the optimal concentration of HCO3− in their cultivation environment. The results showed that the tomato could maintain both the net increase of HCO3− fixation and normal growth, when the maximum concentration of HCO3− in the cultivation surroundings was discovered during the growth period: 25 mmol/L NaHCO3-solution in seed germination, 14 g-NaHCO3/kg-soil in the cotyledon development, 8 to 10 g-NaHCO3/kg-soil during the seedling, 6 g-NaHCO3/kg-soil in the flowering, and 9 g-NaHCO3/kg-soil in the fruiting. However, excessive HCO3− could impair the development of tomato plants, especially the vegetative growth at seedling/flowering stages and the root growth at fruiting stage due to the increased soil pH and EC by HCO3−. On the other hand, H2O produced by the decomposition of HCO3− by tomato plants could alleviate physiological stress under severe conditions. Therefore, HCO3− became the main inorganic carbon source of tomato assimilation under extreme stress. This study provides a data basis for selecting and optimizing the appropriate HCO3− application amount when CO2 is used for agricultural eco-fixation in the form of HCO3− in the future.

Size regulation of the lateral organ initiation zone and its role in determining cotyledon number in conifers.

Unlike monocots and dicots, many conifers, particularly Pinaceae, form three or more cotyledons. These are arranged in a whorl, or ring, at a particular distance from the embryo tip, with cotyledons evenly spaced within the ring. The number of cotyledons, nc, varies substantially within species, both in clonal cultures and in seed embryos. nc variability reflects embryo size variability, with larger diameter embryos having higher nc. Correcting for growth during embryo development, we extract values for the whorl radius at each nc. This radius, corresponding to the spatial pattern of cotyledon differentiation factors, varies over three-fold for the naturally observed range of nc. The current work focuses on factors in the patterning mechanism that could produce such a broad variability in whorl radius. Molecularly, work in Arabidopsis has shown that the initiation zone for leaf primordia occurs at a minimum between inhibitor zones of HD-ZIP III at the shoot apical meristem (SAM) tip and KANADI (KAN) encircling this farther from the tip. PIN1-auxin dynamics within this uninhibited ring form auxin maxima, specifying primordia initiation sites. A similar mechanism is indicated in conifer embryos by effects on cotyledon formation with overexpression of HD-ZIP III inhibitors and by interference with PIN1-auxin patterning. We develop a mathematical model for HD-ZIP III/KAN spatial localization and use this to characterize the molecular regulation that could generate (a) the three-fold whorl radius variation (and associated nc variability) observed in conifer cotyledon development, and (b) the HD-ZIP III and KAN shifts induced experimentally in conifer embryos and in Arabidopsis. This quantitative framework indicates the sensitivity of mechanism components for positioning lateral organs closer to or farther from the tip. Positional shifting is most readily driven by changes to the extent of upstream (meristematic) patterning and changes in HD-ZIP III/KAN mutual inhibition, and less efficiently driven by changes in upstream dosage or the activation of HD-ZIP III. Sharper expression boundaries can also be more resistant to shifting than shallower expression boundaries. The strong variability seen in conifer nc (commonly from 2 to 10) may reflect a freer variation in regulatory interactions, whereas monocot (nc = 1) and dicot (nc = 2) development may require tighter control of such variation. These results provide direction for future quantitative experiments on the positional control of lateral organ initiation, and consequently on plant phyllotaxy and architecture.

Chayote Fruit (Sechium edule var. virens levis) Development and the Effect of Growth Regulators on Seed Germination.

The chayote fruit is a nontraditional vegetable belonging to the Cucurbitaceae family. The fruit has an endocarpic recalcitrant seed that emerges postharvest, drastically shortening its shelf life. In this study, the changes during fruit and seed development before and after harvest (ah) are reported. Additionally, in order to investigate how growth regulators (GRs) affect seed germination, 2-cloroethylphosphonic acid (CPA) (200 µL L-1), gibberellic acid (GA3) (100 and 200 mg L-1), auxin (2,4-D) (0.5 and 1.0 mM), and abscisic acid (ABA) (0.5 and 1.0 mM) were applied after harvest. The results showed that the chayote fruit reached horticultural maturity at 21 days after anthesis, with a sigmoid trend: phase I featured slow growth and high transpiration; in phase II, growth was accelerated and accumulation of endosperm was observed; and in phase III, both growth rate and transpiration were reduced, soluble sugars increased, and the seed showed 25% cotyledon development. At day 13 ah, CPA, GA3, and 2,4-D (0.5 mM) increased seed germination, with values between 10 and 15 mm of the embryonary axis, and the treatments with 2,4-D (1 mM) and ABA (0.5 and 1.0 mM) retarded their growth (2-6 mm). This research allowed us to reveal the phenological phases and the shelf life of the chayote fruit, as well as the results of possible postharvest treatment with GRs; our results suggest that strategies to delay viviparism and prolong the shelf life of the fruit should be applied before 10 days ah, when the embryonic axis of the seed has not developed.

Genome-wide identification of YABBY genes in three Cymbidium species and expression patterns in C. ensifolium (Orchidaceae).

Members of the YABBY gene family play significant roles in lamina development in cotyledons, floral organs, and other lateral organs. The Orchidaceae family is one of the largest angiosperm groups. Some YABBYs have been reported in Orchidaceae. However, the function of YABBY genes in Cymbidium is currently unknown. In this study, 24 YABBY genes were identified in Cymbidium ensifolium, C. goeringii, and C. sinense. We analyzed the conserved domains and motifs, the phylogenetic relationships, chromosome distribution, collinear correlation, and cis-elements of these three species. We also analyzed expression patterns of C. ensifolium and C. goeringii. Phylogenetic relationships analysis indicated that 24 YABBY genes were clustered in four groups, INO, CRC/DL, YAB2, and YAB3/FIL. For most YABBY genes, the zinc finger domain was located near the N-terminus and the helix-loop-helix domain (YABBY domain) near the C-terminus. Chromosomal location analysis results suggested that only C. goeringii YABBY has tandem repeat genes. Almost all the YABBY genes displayed corresponding one-to-one relationships in the syntenic relationships analysis. Cis-elements analysis indicated that most elements were clustered in light-responsive elements, followed by MeJA-responsive elements. Expression patterns showed that YAB2 genes have high expression in floral organs. RT-qPCR analysis showed high expression of CeYAB3 in lip, petal, and in the gynostemium. CeCRC and CeYAB2.2 were highly expressed in gynostemium. These findings provide valuable information of YABBY genes in Cymbidium species and the function in Orchidaceae.

Phenotypically abnormal cotyledonary Vitis vinifera embryos differ in anatomy, endogenous hormone levels and transcriptome profiles.

In many perennial fruit species, including grapevine (Vitis vinifera L.), the highly complex process of somatic embryogenesis (SE) can result in the formation of a deformed embryo, although the underlying reasons are still poorly understood. Here, V. vinifera cv. 'Chardonnay' cotyledonary embryos with distinct morphologies were used to address this issue. Normal cotyledonary embryos (NCEs) and elongated cotyledonary embryos (ECEs) were observed to have better-developed vasculature and shoot meristems than the vitrified cotyledonary embryos (VCEs) and fused cotyledonary embryos (FCEs), but ECEs were less developed. We determined that the morphological differences in these phenotypically abnormal embryos were likely associated with endogenous hormone levels, since concentrations of the phytohormones indoleacetic acid (IAA) and abscisic acid (ABA) in NCEs were higher than in the other three types. Comparative transcriptome analysis revealed large differences in gene expression of the hormone signaling pathways in normal and abnormal cotyledonary embryos. Weighted gene co-expression network analysis of the different cotyledonary types allowed the identification of co-regulated gene modules associated with SE, suggesting a role for ERF family genes and other transcription factors (TFs) in regulating morphology. Moreover, an analysis of morphology-specific gene expression indicated that the activation of a specific protein kinase, small heat shock proteins (sHSPs) and certain TFs was closely associated with the formation of normal cotyledonary embryos. Our comparative analyses provide insights into the gene networks regulating somatic cotyledon development and open new avenues for research into plant regeneration and functional genomic studies of malformed embryos.

Amino acids induce high seed-specific expression driven by a soybean (Glycine max) glycinin seed storage protein promoter.

We characterize GFP expression driven by a soybean glycinin promoter in transgenic soybean. We demonstrate specific amino acid-mediated induction of this promoter in developing soybean seeds in vitro. In plants, gene expression is primarily regulated by promoter regions which are located upstream of gene coding sequences. Promoters allow transcription in certain tissues and respond to environmental stimuli as well as other inductive phenomena. In soybean, seed storage proteins (SSPs) accumulate during seed development and account for most of the monetary and nutritional value of this crop. To better study the regulatory functions of a SSP promoter, we developed a cotyledon culture system where media and media addenda were evaluated for their effects on cotyledon development and promoter activity. Stably transformed soybean events containing a glycinin SSP promoter regulating the green fluorescent protein (GFP) were generated. Promoter activity, as visualized by GFP expression, was only observed in developing in planta seeds and in vitro-cultured isolated embryos and cotyledons from developing seeds when specific media addenda were included. Asparagine, proline, and especially glutamine induced glycinin promoter activity in cultured cotyledons from developing seeds. Other amino acids did not induce the glycinin promoter. Here, we report, for the first time, induction of a reintroduced glycinin SSP promoter by specific amino acids in cotyledon tissues during seed development.

Pydiflumetofen: An SDHI seed‐applied fungicide, a potential tool for the canola‐blackleg management toolbox

AbstractBlackleg is a major fungal disease of canola caused by Leptosphaeria maculans. Due to the breakdown of current host resistance, having an effective fungicide to avoid seedling infection is important to avoid disease. Pydiflumetofen is a newly developed broad‐spectrum seed treatment fungicide in the succinate dehydrogenase inhibitor (SDHI) group. We evaluated the separate and combined application of pydiflumetofen and Vibrance Flexi on early‐season control of blackleg using moderately resistant canola cultivar SY4135 and susceptible cultivar Westar. In the greenhouse, seedlings inoculated with green fluorescent protein (GFP)‐tagged L. maculans showed lesion development and apoplastic mycelial growth in cotyledons in control and Vibrance Flexi treatments but no lesion development or in planta mycelial growth was observed in pydiflumetofen‐treated seedlings, in Westar or SY4135, 14 days postinoculation. SY4135 and Westar plants with pydiflumetofen‐treated seeds inoculated with L. maculans isolate D3 had significantly lower disease severity. Both host genotypes treated with pydiflumetofen showed lower disease severity estimates than the other treatments. Statistically significant disease severity reduction was cultivar dependent in the field. Canola is most susceptible to blackleg as a seedling, from the cotyledon to two‐ to four‐leaf stage. Pydiflumetofen protects the plant at the critical window for infection. Therefore, pydiflumetofen could be a potential tool that farmers can add to their blackleg management toolbox.

Monitoring of cocoa post-harvest process practices on a small-farm level at five locations in Ecuador

Cocoa post-harvest practices were monitored on a small-farm scale (ca. 50 kg fresh beans) at five intermediaries from four provinces in Ecuador: (A) in Manabí, (B) and (E) in Los Ríos, (C) in Cotopaxi, (D) in Guayas. Temperature, pH (pulp, cotyledon), cell counts (yeasts, lactic acid bacteria, acetic acid bacteria) were recorded daily, and cut-tests and sensory descriptive analysis evaluated end quality. An overall inconsistency and variability in processing were observed with different fermentation devices (jute/plastic bags, wooden boxes), pre-drying, turning during fermentation, fermentation duration, and different drying processes (temperatures, direct/indirect). Key parameters (maximum temperature, pH cotyledon development) revealed a significant impact of the fermentation device on the post-harvest process and, therefore, on the fermentation development. 67–74 h in jute bags without turning was sufficient to reach well-fermented cocoa beans without moldy off-flavors, whereas 133 h in plastic bags without turning resulted in 3 ± 1% moldy beans and cocoa liquor with moldy off-flavor. Drying at high temperatures (80 ± 10 °C) with direct heat contact resulted in beans roasted to burnt off-flavor. Conclusively, the whole post-harvest process was crucial for well-fermented beans without off-flavor. Plastic bags seemed unsuitable, while jute bags could be an alternative to wooden boxes.

BBX16 mediates the repression of seedling photomorphogenesis downstream of the GUN1/GLK1 module during retrograde signalling.

Summary Plastid‐to‐nucleus retrograde signalling (RS) initiated by dysfunctional chloroplasts impact photomorphogenic development. We have previously shown that the transcription factor GLK1 acts downstream of the RS regulator GUN1 in photodamaging conditions to regulate not only the well established expression of photosynthesis‐associated nuclear genes (PhANGs) but also to regulate seedling morphogenesis. Specifically, the GUN1/GLK1 module inhibits the light‐induced phytochrome‐interacting factor (PIF)‐repressed transcriptional network to suppress cotyledon development when chloroplast integrity is compromised, modulating the area exposed to potentially damaging high light. However, how the GUN1/GLK1 module inhibits photomorphogenesis upon chloroplast damage remained undefined.Here, we report the identification of BBX16 as a novel direct target of GLK1. BBX16 is induced and promotes photomorphogenesis in moderate light and is repressed via GUN1/GLK1 after chloroplast damage. Additionally, we showed that BBX16 represents a regulatory branching point downstream of GUN1/GLK1 in the regulation of PhANG expression and seedling development upon RS activation.The gun1 phenotype in lincomycin and the gun1‐like phenotype of GLK1OX are markedly suppressed in gun1bbx16 and GLK1OXbbx16.This study identified BBX16 as the first member of the BBX family involved in RS, and defines a molecular bifurcation mechanism operated by GLK1/BBX16 to optimise seedling de‐etiolation, and to ensure photoprotection in unfavourable light conditions.

Overexpression of the LcCUC2-like gene in Arabidopsis thaliana alters the cotyledon morphology and increases rosette leaf number.

BackgroundThe unique ‘mandarin jacket’ leaf shape is the most famous trait of Liriodendron chinense and this characteristic gives L. chinense aesthetic and landscaping value. However, the underlying regulatory mechanism of genes involved in the leaf development of L. chinense has remained unclear.MethodsBased on transcriptome data of leaves at different developmental stages from L. chinense, we identified differentially expression genes (DEGs) functioning in leaf development. A candidate gene named LcCUC2-like (LcCUC2L) had high similarity in sequence with Arabidopsis thaliana CUC2, and used for further research. We isolated the full-length LcCUC2L gene and its promoter from L. chinense. Subsequently, we analyzed the function of the LcCUC2L gene and its promoter activity via transformation into A. thaliana.ResultsIn this study, we found that the LcCUC2L and AtCUC2 are homologous in sequence but not homologous in function. Unlike the role of AtCUC2 in leaf serration and SAM formation, the LcCUC2L mainly regulates cotyledon development and rosette leaf number. Histochemical β-glucuronidase (GUS) staining revealed that LcCUC2L was expressed in the cotyledons of A. thaliana seedlings, indicating that the LcCUC2L may play a role in cotyledon development. Ectopic expression of LcCUC2L resulted in long, narrow cotyledons without petioles, abnormal lamina epidermis cells and defective vascular tissue in cotyledons, and these results were consistent with the LcCUC2L expression pattern. Further analysis showed that overexpression of LcCUC2L also induced numerous rosette leaves. Also, LcCUC2L and other related genes showed a severe response in L. chinense by introducing exogenous auxin stimulation, partly revealed that LcCUC2L affects the leaf development by regulating the auxin content.ConclusionsThese results suggest that LcCUC2L may play a critical role in leaf development and morphogenesis in L. chinense, and our findings provide insight into the molecular mechanisms of leaf development in L. chinense.

Biochar mitigation of allelopathic effects in three invasive plants: evidence from seed germination trials

Many invasive species show allelopathic effects that contribute to competitive impacts on native vegetation for which few control measures exist. We investigated the potential for pyrolized organic material used as a soil amendment (“biochar”) to sorb allelochemicals and mitigate allelopathic effects on seed germination and early seedling development in three common invasive plants in Canada: garlic mustard (Alliaria petiolata), tree of heaven (Ailanthus altissima), and yellow sweetgrass (Melilotus officinalis). We hypothesized that biochars would mitigate effects on germination and early seedling development (radicle extension and cotyledon development) through sorption of allelochemicals. Laboratory assays of seed germination and early seedling development of two agricultural crops (Lactuca sativa and Raphinus raphanistrum) and two native grass species (Andropogon gerardi and Poa palustris) were conducted using water extracts from leaves. Seeds were treated with plant extracts exposed to four different biochars (red oak (Quercus rubra), jack pine (Pinus banksiana), shipping pallet and construction waste, and high-carbon wood ash) using a range of extract and biochar dosages. Treatment of allelopathic plant extracts by biochars significantly (p < 0.05) mitigated effects on seed germination for Alliaria and Melilotus. Effects on seed germination and early seedling development depended on extract concentration, biochar dosage, and the target species assessed. Controls treated with biochar leachate alone showed significantly (p < 0.05) increased germination for two of the biochars tested (jack pine biochar and high-carbon wood ash). Results indicated that biochars can mitigate allelopathic effects of invasive species through sorption of allelochemicals; however, this will be effective in only some cases.

An Amur grape VaHsfC1 is involved in multiple abiotic stresses

Plant heat stress transcription factors (Hsfs) belong to a very large gene family and play dominant roles in response to heat stress. Here, we report the functional analysis of VaHsfC1, a class C Hsf gene from Vitis amurensis, and involved in multiple abiotic stresses. The structure of VaHsfC1 contains a typical HSF domain for DNA-binding at N terminus. Phylogenetic analysis revealed that VaHsfC1 belongs to the C1 family of Hsfs. VaHsfC1 was highly induced by heat, cold, exogenous abscisic acid (ABA) and salinity, respectively. Unusually, VaHsfC1was preferentially localized in nucleus, but less in the cytosol. Also, no transcriptional activation was detected for the protein in yeast cells. Ectopic VaHsfC1 expression in Arabidopsis enhanced heat tolerance characterized by the increased survival rate, higher chlorophyll content, reduced electrolyte leakage, and activated expressions of ascorbate peroxidase (Apx2) and heat shock protein (HSP) expression compared to the WT. Interestingly, overexpression of VaHsfC1 in Arabidopsis could also increase the cold tolerance, as reveled from a series changes at the physiological and biochemical steps, as well as at the transcript levels of CORs in the CBF-dependent responsive pathway. Additionally, the growth of VaHsfC1-overexpressing Arabidopsis showed enhanced seed ABA hypersensitivity during germination and cotyledon development, and a significant reduction in stomatal aperture was also observed in overexpression lines. Furthermore, VaHsfC1-overexpressing lines displayed salt-hypersensitive phenotype with a lower rates both in germination and cotyledon greening, and the inhibition of root growth. Our findings demonstrated that the complex nature of VaHsfC1 in mediating multiple abiotic stress responses, as a key component to further understanding of the ‘crosstalk’ mechanism of multiple abiotic stress response in plants.