Effect of 2,4-dichlorophenoxyacetic acid on callus induction and plant regeneration in anther culture of wheat (Triticum aestivum L.)

Phytochemical Profiles and Cytotoxic Activity of Bursera fagaroides (Kunth) Engl. Leaves and Its Callus Culture

Bursera fagaroides, popularly used in México, possesses bioactive lignans. These compounds are low in the bark, and its extraction endangers the life of the trees. The aim of the present investigation was to search for alternative sources of cytotoxic compounds in B. fagaroides prepared as leaves and in vitro callus cultures. The friable callus of B. fagaroides was established using a combination of plant growth regulators: 4 mgL-1 of 2,4-dichlorophenoxyacetic acid (2,4-D), 1 mgL-1 Naphthaleneacetic Acid (NAA) and 1 mgL-1 Zeatin. The maximum cell growth was at day 28 with a specific growth rate of μ = 0.059 days-1 and duplication time td = 11.8 days. HPLC quantification of the dichloromethane callus biomass extract showed that Scopoletin, with a concentration of 10.7 µg g-1 dry weight, was the main compound inducible as a phytoalexin by the addition of high concentrations of 2,4-D, as well as by the absence of nutrients in the culture medium. In this same extract, the compounds γ-sitosterol and stigmasterol were also identified by GC-MS analysis. Open column chromatography was used to separate and identify yatein, acetyl podophyllotoxin and 7',8'-dehydropodophyllotoxin in the leaves of the wild plant. Cytotoxic activity on four cancer cell lines was tested, with PC-3 prostate carcinoma (IC50 of 12.6 ± 4.6 µgmL-1) being the most sensitive to the wild-type plant extract and HeLa cervical carcinoma (IC50 of 72 ± 5 µgmL-1) being the most sensitive to the callus culture extract.

An Efficient Genetic Transformation and CRISPR/Cas9-Based Genome Editing System for Moso Bamboo (Phyllostachys edulis)

Moso bamboo (Phyllostachys edulis) is the most important monopodial bamboo species worldwide. Without a genetic transformation system, it is difficult to verify the functions of genes controlling important traits and conduct molecular breeding in moso bamboo. Here, we established a plant regeneration system from immature embryos. Calli were induced on MS medium added 4-6 mg⋅L-1 2,4-dichlorophenoxyacetic acid (2,4-D) with high efficiency (>60%). A plant growth regulator combination of 0.5 mg⋅L-1 1-naphthylacetic acid (NAA), 2.0 mg⋅L-1 6-benzylaminopurine (BAP), and 3.0 mg⋅L-1 zeatin (ZT) was suitable for shoot differentiation, and the shoot induction frequency was increased to 43% after 0.5 mg⋅L-1 abscisic acid (ABA) pretreatment. An effective antibiotic screening concentration was determined by hygromycin sensitivity test. We further optimized the Agrobacterium concentration and added vacuum infiltration for infection, which improves the transient expression efficiency. A genetic transformation system was established for the first time in moso bamboo, with the transformation efficiency of approximately 5%. To optimize genome editing, two endogenous U3 small nuclear RNA (snRNA) promoters were isolated and used to drive small guide RNA (sgRNA) expression. The results showed that the PeU3.1 promoter exhibited higher efficiency, and it was used for subsequent genome editing. Finally, homozygous pds1pds2 mutants were obtained by an efficient CRISPR/Cas9 genome-editing system. These technical systems will be conducive to gene functional validation and accelerate the molecular breeding process of moso bamboo.

Agrobacterium-Mediated Genetic Transformation of Taiwanese Isolates of Lemna aequinoctialis

Duckweed (Lemna aequinoctialis) is one of the smallest flowering plants in the world. Due to its high reproduction rate and biomass, duckweeds are used as biofactors and feedstuff additives for livestock. It is also an ideal system for basic biological research and various practical applications. In this study, we attempt to establish a micropropagation technique and Agrobacterium-mediated transformation in L. aequinoctialis. The plant-growth regulator type and concentration and Agrobacterium-mediated transformation were evaluated for their effects on duckweed callus induction, proliferation, regeneration, and gene transformation efficiency. Calli were successfully induced from 100% of explants on Murashige and Skoog (MS) medium containing 25.0 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 2.0 μM thidiazuron (TDZ). MS medium containing 4.5 μM 2,4-D and 2.0 μM TDZ supported the long-lasting growth of calli. Fronds regenerated from 100% of calli on Schenk and Hildebrandt (SH) medium containing 1.0 μM 6-benzyladenine (6-BA). We also determined that 200 μM acetosyringone in the cocultivation medium for 1 day in the dark was crucial for transformation efficiency (up to 3 ± 1%). Additionally, we propose that both techniques will facilitate efficient high-throughput genetic manipulation in Lemnaceae.

Haploid Embryogenesis in Isolated Microspore Culture of Carrots (Daucus carota L.)

The process of embryogenesis in isolated microspore culture was studied in eight carrot accessions of different origin. The ½NLN-13 medium supplemented with 0.2 mg/L 2,4D and 0.2mg/L kinetin was used to induce embryogenesis. The temperature treatment was performed at 5–6 °C for three days, followed by cultivation at 25 °C in darkness. As was shown, the first embryogenesis was only observed in microspores at the late vacuolated stage when the nucleus moved from the center to one pole following the long cell axis. Depending on the nucleus position, the microspore can divide into two equal or two different sized cells. Following divisions occurred either in one of these cells or in two. However, microspores that divided into two unequal cells were morphologically different form bi-cellular pollen grain. Embryogenic divisions in bi-cellular pollen grains were not observed. First divisions began by the third day of cultivation, and continued until the globular embryoid stage that was well-seen after the fourth week of cultivation. The already-formed embryoids can develop the secondary embryoids on their surface. Depending on the genotype, up to 1000 secondary embryoids can be produced from one embryoid in the liquid MSm medium supplemented with 0.1 mg/L of kinetin for regeneration. All carrot accessions studied were split into three groups: responsive genotypes, weakly responsive genotypes, and reluctant genotypes. The highest yield was 53 initial embryoids per a 6 cm diameter petri dish. Thus, the Nantskaya 4 cultivar totally produced 256 initial embryoids, out of which 94 developed into green plantlets and 162 into albino plantlets, whereas 97 initial embryoids with 45 albino plantlets formed from them were obtained from Chantenay cultivar.

Comparison of the Androgenic Response of Spring and Winter Wheat (Triticum aestivum L.)

Androgenesis is potentially the most effective technique for doubled haploid production of wheat. It is not however widely used in breeding programmes due to its main limitation: the genotype dependence. Due to genetic differences between spring and winter wheat, it was assumed that both phenotypes are different in their capacity to conduct androgenesis. And so, the aim of this investigation was to verify the effectiveness of androgenesis induction and plant regeneration of spring and winter wheat genotypes while considering varying amounts of growth hormones in the induction medium. Fifteen genotypes of spring wheat and fifteen of winter wheat were used in the experiment. Six hundred anthers of each of the 30 genotypes were plated and analysed. Previous studies have allowed selection of the best medium for wheat androgenesis and a combination of growth hormones that are the most effective in stimulating microspore proliferation. Therefore, C17 induction media with two combinations of growth hormones were used: I—supplemented only by auxins (2,4-D and dicamba), and II—supplemented by auxin and cytokinin (2,4-D and kinetin). Data was recorded according to the efficiency of androgenic structure formation (ASF), green plant regeneration (GPR), and albino plant regeneration (APR). The results showed that the induction and regeneration of androgenesis in the spring wheat were more efficient than in the winter ones. The spring genotypes formed more androgenic structures and green plants on anthers plated on the medium supplemented only by auxins, in contrast to the winter genotypes which were better induced and regenerated on the medium supplemented by auxin and cytokinin. The study showed that to increase the efficiency of androgenesis, it is necessary to select appropriate factors such as concentration and type of hormones in medium composition, affecting the course of the culturing procedure according to the winter or spring phenotype of donor plants.

Effect of Zearalenone and Hormone Regulators on Microspore Embryogenesis in Anther Culture of Wheat

The purpose of this work was to assess the impact of zearalenone (ZEN) and selected hormone regulators on the effectiveness of microspore embryogenesis in anther culture of wheat. The plant material comprised F₁ hybrids of winter and spring wheat. Six combinations of media inducing microspore proliferation and formation of embryogenic structures were investigated: two combinations of growth regulators (D - 2,4-D + dicamba, K - 2,4-D + kinetin), each with three ZEN concentrations (0 mL/L, 0.1 mL/L, 0.2 mL/L). A significant increase in microspore embryogenesis effectiveness on media with the addition of ZEN was observed both at the stages of its induction and the formation of green plants in some genotypes. In case of both combinations of growth regulators, an increased concentration of ZEN resulted in more effective induction of microspore embryogenesis. The most effective induction medium was the D medium supplemented with 0.2 mL/L ZEN. As a result of the use of zearalenone together with two combinations of growth regulators, all genotypes tested produced androgenic structures, which indicates the breakdown of genotypic recalcitrant in the analysed hybrids. In addition, green plants were obtained from 18 out of 19 tested hybrids. The addition of ZEN to the medium did not affect the number of regenerated albino plants nor the number of spontaneous genome doublings proportion.

Modeling callus induction and regeneration in an anther culture of tomato (Lycopersicon esculentum L.) using image processing and artificial neural network method

Doubled haploids, subsequent to haploid induction, have wide range of applications in basic and applied plant studies. Various parameters can affect the efficiency of haploid induction through an anther culture of tomato. The hybrid system of image processing-artificial neural network (ANN) was used to better understand callus induction and regeneration in an anther culture of tomato. The effect of parameters such as plant genotype, the concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin (Kin) plant growth regulators, the concentration of gum arabic (GA) additive, the cold pretreatment duration, and flower length on callus induction percentage and number of regenerated calli in an anther culture of tomato were studied using multiple linear regression (MLR) and ANN models. The precise flower bud length was measured using an image processing technique. The 4',6-diamidino-2-phenylindole (DAPI) analysis showed that the flowers with 5-6.9 mm length had the highest percentage of the mid- to late-uninucleate microspore stage. The best ANN model for both callus induction percentage and number of regenerated calli was a model with one hidden layer, 12-15 neurons in the first hidden layer, Levenberg-Marquardt learning algorithm, and Tan-Sigmoid transfer function in hidden layer, based on the root mean square error (RMSE), mean absolute error (MAE), and coefficient of determination (R²) statistics. The scatter plot of measured values versus the predicted values showed the superiority of the ANN to MLR model to predict the callus induction percentage in an anther culture of tomato. The sensitivity analysis of MLR and ANN models revealed the plant genotype and 2,4-D concentration as the most important factors affecting both callus induction percentage and number of regenerated calli. Since tomato is a recalcitrant plant to androgenesis-based pathway of haploid induction, therefore the results of the present study can be helpful to develop an efficient haploid induction protocol in tomato through an anther culture pathway.

Development of a new wheat germplasm with high anther culture ability by using a combination of gamma-ray irradiation and anther culture

BACKGROUND

Wheat with high anther culture ability would be beneficial for breeding. We aimed to screen a wheat germplasm to with high anther culture ability as well as good agronomic characteristics.

RESULTS

The F1 young spikes of winter wheat cross combination Yanfu188/Jimai37 were irradiated with gamma rays at a dose of 1.5 Gy to develop a new germplasm H307 with high anther culture ability. The proportion of green plantlets per 100 anthers (GP/100A) of H307 was 14.50% which was higher than other H2 lines (P < 0.05). Analysis over three successive years (2006-2008) revealed that the green plantlet regeneration ability of H307 remained high in all 3 years. Reciprocal crosses between H307 and Nongda3308 showed no significant differences in their values for calli per 100 anthers (CA/100A), green plantlets per 100 calli (GP/100C) and GP/100A (P > 0.05). Five main wheat varieties used in production, namely Yumai68, Yanzhan4110, Bainongaikang58, Zhoumai18 and Xinmai18, were selected to cross with the new H307. CA/100A, GP/100C and GP/100A were used to assess the anther culture ability of F1 hybrids, demonstrating that the anther culture ability of H307 was heritable.

CONCLUSION

H307 possessed high anther culture ability that was heritable, which would be potential germplasm for improving wheat anther breeding ability.

Differences in surface behaviour of galactolipoids originating from different kind of wheat tissue cultivated in vitro

The aim of presented researches was to investigate the physicochemical properties of Langmuir monolayer of galactolipids extracted from two different kinds of plastids: immature embryos and inflorescences. Differences between the physicochemical properties of the plastid membranes may help to explain different physiological processes, such as plant regeneration. Surface pressure (pi) vs. molecular area (A) isotherms of the monogalactosyldiacylglycerol (MGDG)/digalactosyldiacylglycerol (DGDG) monolayers of various molar ratios were measured at 15 degrees C. Galactolipids were extracted from two different types of tissue: inflorescences and embryos. Based on the analysis of the pi-A isotherms, the properties of monolayers, such as collapse pressure (pi(coll)), limiting area (A(lim)), compressibility modulus (C(s)(-1)), excess free energy of mixing (DeltaG(EXC)) and free energy of mixing (DeltaG(MIX)), were calculated. The results show that pure MGDG and DGDG and their mixtures form liquid-expanded monolayers, independently on the kind of tissue. Galactolipids originating from inflorescences produce more compressible films at the air/water interface, with larger limiting area per molecule and lower stability against the collapse process. MGDG and DGDG are miscible and form non-ideal mixed monolayers at the air/water interface. Negative values of DeltaG(EXC) were calculated for the mixture of galactolipids originating from inflorescences, with the content of MGDG, x(MGDG)>0.6. In the case of embryos, the negative values of DeltaG(EXC) were found for x(MGDG) approximately 0.5. Therefore, the attractive interactions between MGDG and DGDG exist in the mixtures of these compositions. As it is shown by negative values of DeltaG(MIX), mixed monolayers are more stable compared with unmixed ones.