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Research Article, J Plant Physiol Pathol Vol: 7 Issue: 2

The Effects of Growth Regulators and Illumination Intensity on Anthocyanins Production in Psammosilene tunicoides Callus

Hong-Bian Wei, Yan-Yan Gao, Ming-Sheng Zhang*, Xiao- Hong Wang, Xue Li, Li Tian, Si-Jia Liu and Jian-Dong Liu

School of Life Sciences, Key Laboratory of Plant Resources Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), Guizhou University, Guiyang, 550025 Guizhou, People’s Republic of China

*Corresponding Author : Ming-Sheng Zhang
School of Life Sciences, Key Laboratory of Plant Resources Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), Guizhou University, 14, Xia-hui Rd., Guiyang City, China
Fax: 86-851-83856374
E-mail: [email protected]

Received: February 12, 2019 Accepted: March 28, 2019 Published: April 05, 2019

Citation: Wei H, Gao Y, Zhang M, Wang X, Li X, et al. (2019) The Effects of Growth Regulators and Illumination Intensity on Anthocyanins Production in Psammosilene tunicoides Callus. J Plant Physiol Pathol 7:2. doi: 10.4172/2329-955X.1000199

Abstract

Psammosilene tunicoides. In this study, the stems, leaves and buds of P. tunicoides were used as explants, adding growth regulators (NAA, 2,4-D and 6-BA) in MS basic medium, and by adjusting the concentrations of growth regulators and the illumination intensity in culture room to induce callus, then the proliferated callus were used to extract anthocyanins. The results showed that the callus induction rate was the highest using buds as explants; it was about 1 to 2 times high of others (stems and leaves). NAA or 6-BA contributed to induce anthocyanins synthesis in the white callus. With the increase of 6-BA concentration, the anthocyanins content increased after slightly decreased, and the anthocyanins synthesis was promoted by increasing NAA concentration from 0.5 mg·L-1 to 1.5 mg·L-1 but decreased thereafter up to 2.5 mg·L-1. The combination screening of growth regulators indicated that the combination of 1.5 mg·L-1 NAA+0.5 mg·L-1 6-BA was the appropriate condition in the range of 0.5 mg·L-1 to 2.5 mg·L-1. The illumination intensity of 2000 lx was fit for anthocyanins formation in callus. The anthocyanins synthesis in callus was repressed when 2,4-D was added into medium. The results will provide reference for the pigments production in callus culture of P. tunicoides.

Keywords: Psammosilene tunicoides; Tissue culture; Callus, Anthocyanins; Growth regulator; Illumination intensity

Abbreviations

2,4-D: 2,4-Dichlorophenoxyacetic Acid; 6-BA: 6-Benzylaminopurine; Abs: Absorbance; DW: Dry Weight; FW: Fresh Weight; MS: Murashige and Skoog Medium; NAA: α-Naphthaleneacetic Acid

Introduction

Psammosilene tunicoides is a single-species genera and Chinese endemic plant; it is also a rare and extinct medicinal plant with high medicinal value. In addition to the root can be used as medicine, its stems, leaves and flowers contain amounts of anthocyanins (secondary metabolites in plants). In recent years, plant anthocyanins have been gradually favored by people because of their prominent effects in anti-oxidation [1], anti-inflammation [2], anti-tumor [3], anti-cancer [4] and cardioprotection [5,6]. Anthocyanins are abundant in plant of P. tunicoides, but the production of anthocyanins from P. tunicoides has not been reported yet.

Anthocyanins belong to the plant secondary metabolites exist widely in plant roots, stems, leaves, flowers, fruits and storage organs with colors from scarlet to blue. But extraction of the anthocyanins from plant is often tedious and expensive as the plant is seasonal, and it is also devastating. It is a good method to produce anthocyanins by plant callus culture, and some reports have been made on this aspect [7-10].

In vitro induction of pigments in plant tissue culture is dependent on the culture medium, temperature, pH, rate of aeration, and level of illumination [11]. Earlier studies indicated that induction of anthocyanins was influenced strongly by high sucrose concentration [12] and low NH4+ nitrogen concentration in the suspension culture media [13]. Most in vitro studies have shown evidence for some effects of light on the pigments accumulation in cultured cells [14]. Others demonstrated that auxin alone significantly inhibited anthocyanins biosynthesis, but co-culture of auxin and cytokinin increased significantly the anthocyanins levels [15]. Therefore, in this test, the authors explored the effects with auxin (NAA, 2,4-D), cytokinin (6-BA) and illumination intensity for anthocyanins biosynthesis in callus culturesof P. tunicoides, so as to provide a theoretical basis for sustainable development and utilization of the anthocyanins resourcesfrom P. tunicoides.

Materials and Methods

Induction of white callus

The young stems, leaves and buds from asepsis seedlings of P. tunicoides were inoculated on MS basic medium [16] containing 2,4-D (0.5 to 1.5 mg·L-1), 6-BA (0.5 to 2.0 mg·L-1), sucrose (30 g·L-1) and agar (7 g·L-1) by orthogonal experiment L9(33) (Table 1). The pH of the medium was adjusted to 5.8 before autoclaving at 121°C for 20 min. The culture conditions were (25 ± 1)°C and illumination intensity of 1000 lx with 12 h·d-1 photoperiod. The explants were placed respectively on Petri dishes containing MS medium, 5 explants per Petri dish with five repetitions for callus induction. After 25 days, significant differences among the treatments were estimated by analysis of variance (ANOVA).

Serial number Explants(g) 2,4-D (mg·L-1) 6-BA (mg·L-1) FW (g)
1 Leaves 0.5 0.5 1.07 cde
2 Leaves 1.0 1.0 1.76 bcd
3 Leaves 1.5 2.0 0.33 e
4 Stems 1.0 0.5 0.89 de
5 Stems 1.5 1.0 0.79 de
6 Stems 0.5 2.0 0.99 de
7 Buds 1.5 0.5 2.08 abc
8 Buds 0.5 1.0 3.11 a
9 Buds 1.0 2.0 2.71 ab
Means with different letters indicate significant level at p=0.05.

Table 1: The callus induction of P. tunicoides by L9(33).

Induction of anthocyanins by growth regulators

This study determined the optimal conditions of pigment production using auxin (NAA) and cytokinin (6-BA). The experiments concerning anthocyanins induction in the white callus were performed on MS medium supplemented 30 g·L-1 sucrose and combining different concentrations growth regulators (6-BA and NAA), addition of 6-BA and NAA ranging from 0 to 2.5 mg·L-1 in increments of 0.5 mg·L-1 (Table 2).

6-BA (mg·L-1) FW (g) Abs NAA (mg·L-1) FW (g) Abs
0.5 1.97 ± 0.03a 0.396 ± 0.01a 0.5 2.13 ± 0.1a 0.326 ± 0.03a
1.0 1.51 ± 0.06b 0.402 ± 0.02a 1.0 2.08 ± 0.1b 0.216 ± 0.03b
1.5 1.26 ± 0.06c 0.384 ± 0.02ab 1.5 1.99 ± 0.08bc 0.226 ± 0.03b
2.0 1.01 ± 0.05d 0.276 ± 0.04bc 2.0 1.80 ± 0.09c 0.174 ± 0.03b
2.5 0.96 ± 0.06d 0.191 ± 0.03c 2.5 1.65 ± 0.07c 0.098 ± 0.02c
Data represents mean value ± standard deviation (SD), means with different letters indicate significant level at p=0.05. The same as below.

Table 2: Effects of different concentrations 6-BA or NAA on fresh weight of callus and anthocyanin induction of P. tunicoides.

Induction of anthocyanins by illumination intensity

This experiment was based on the callus which cultivated on MS medium with 1.5 mg·L-1 NAA and 0.5 mg·L-1 6-BA, and then set different illumination intensity (0, 500, 1000, 1500, 2000, 2500 lx) to induce anthocyanins. Each illumination intensity treatment with 10 Petri dishes which were inoculated fresh callus (each Petri dish contained 0.5 gram callus) and light-dark cycle of 12 h.

Determination of callus growth

The growth of callus was monitored by determination of fresh and dry biomass. Using filter paper to absorb the surface water on the callus, just until the point when free liquid was no longer expressed in paper and then to record fresh weight (FW). After that, the callus was dried in high temperature drying oven for 24 h, then the dry weight (DW) was calculated.

Extraction of anthocyanins

Weighing 2 gram of fresh callus used to extract anthocyanins, and extraction solvent was 1.0% HCl-MeOH (1:50 w/v). Treating callus was extracted overnight in test tube (25 mL) at 4°C for anthocyanins measurement [17]. The extract was filtered through filter paper to 10 mL brown glass flask volumetric, and anthocyanins content was expressed from absorbance measurement.

Statistical analysis

During the white callus induction phase, the total number and fresh/dry weight of callus in each treatment were counted. During the anthocyanins production phase, the weight of callus which had induced and accumulated anthocyanins were counted to calculate the average anthocyanins content of each treatment. But in this paper, we adopted the direct method (A=A530) to determinate the content of anthocyanins in the same solvent [18]. All extracts were prepared in triplicate. In order to find the characters conditions of anthocyanins production, a P-value<0.05 was considered statistically significant by Tukey’s post hoc text. Correlation was evaluated using the Pearson correlation analysis. All experimental data were expressed as means ± standard deviation (SD) of five independent replications.

Results and Discussion

Effects of explants and growth regulators for callus induction

The callus initiated from different explants was slight red color and friable on media containing different factors, which combination leading optimal callus formation of P. tunicoides. It was indicated that the explants with the treatment of cut were inducted to produce callus after one week, and the callus of buds grew obviously better than others (A, B, C in Figure 1). Because the suitable conditions for promoting anthocyanins production in callus were not provided at this stage, the anthocyanins contents in callus were less and the colors of callus were lighter (almost white after 25 days).

Figure 1: Callus from different explants (A: leaves; B: stems; C: buds); the influence of different concentration 6-BA and NAA to anthocyanins induction (D: 2.0 mg·L-1 6-BA+1.0 mg·L-1 NAA; E: 0.5 mg·L-1 6-BA+1.0 mg·L-1 NAA; F: 0.5 mg·L-1 6-BA+1.5 mg·L-1 NAA).

The result showed that the main influence factor of callus induction was explants (Serial No. 7 to 9 in Table 1). The great number of callus formation was obtained in 0.5 mg·L-1 2,4-D and 1.0 mg·L-1 6-BA, which the callus fresh weight was 3.11 g (Serial No. 8 in Table 1). The result not much differed from those of [19], who obtained callus from young stems of P. tunicoides on MS medium supplemented with various hormones in dark condition. In the inoculation of buds media, the biomass for callogenesis were well and quickly. The callus was soft in texture, friable in structure and white in color after 25 days. Callus induction from various tissues was different [20]. The article was reported that soft and friable callus were developed from shoot primordia, hard and compact callus developed from 2 weeks old buds of Zingiber officinale cultured on MS medium [21].

Effects of growth regulators for anthocyanin induction in callus

The effects of hormones combinations for anthocyanins induction in plants culture has previously been reported [22], but it has no reported that induce anthocyanins from P. tunicoides. In this study, it has been recognized that anthocyanins induction and formation in P. tunicoides callus can be regulated by 6-BA, NAA or 6-BA and NAA combination. NAA or 6-BA alone inhibited significantly the multiplication of callus and the induction of anthocyanins with the increase of its concentration (Table 2), but the co-treatment both NAA and 6-BA promoted significantly callus growth and anthocyanins formation (Table 3), and 0.5 mg·L-1 6-BA and 1.5 mg·L-1 NAA was the best combination (Serial No. 11 in Table 3), this result is consistent with which co-treatment of auxin and cytokinin would significantly enhance the anthocyanins [15] And the same time, according to the spectrogram of pigment extracting liquid of P. tunicoides callus, we found the anthocyanins characteristic absorption peak (n=529.0355, Figure 2).

Serial number NAA(mg·L-1) 6-BA(mg·L-1) FW(g) Abs
1 0.5 0.5 2.09 ± 0.02ab 0.43 ± 0.05ab
2 0.5 1.0 2.39 ± 0.12a 0.40 ± 0.05abc
3 0.5 1.5 2.07 ± 0.03ab 0.43 ± 0.02ab
4 0.5 2.0 1.37 ±0.05ef 0.41 ± 0.02ab
5 0.5 2.5 0.84 ± 0.07j 0.40 ± 0.04abc
6 1.0 0.5 1.86 ± 0.11abc 0.38 ± 0.04abc
7 1.0 1.0 2.13 ± 0.12ab 0.25 ± 0.04bc
8 1.0 1.5 2.08 ± 0.03ab 0.32 ± 0.02bc
9 1.0 2.0 1.58 ± 0.09cd 0.13 ± 0.01d
10 1.0 2.5 0.97 ± 0.07ij 0.15 ± 0.03d
11 1.5 0.5 2.43 ± 0.08a 0.57 ± 0.05a
12 1.5 1.0 1.68 ± 0.04bc 0.29 ± 0.03bc
13 1.5 1.5 1.55 ± 0.03de 0.44 ± 0.04ab
14 1.5 2.0 1.32 ± 0.07fj 0.43 ± 0.02ab
15 1.5 2.5 1.21 ± 0.10jh 0.35 ± 0.04bc
16 2.0 0.5 1.82 ± 0.06bc 0.43 ± 0.03ab
17 2.0 1.0 2.03 ± 0.03ab 0.15 ± 0.03d
18 2.0 1.5 1.14 ± 0.12jh 0.36 ± 0.04bc
19 2.0 2.0 1.03 ± 0.07ij 0.36 ± 0.03bc
20 2.0 2.5 0.95 ± 0.10ij 0.20 ± 0.03cd
21 2.5 0.5 1.79 ± 0.13bc 0.33 ± 0.07bcd
22 2.5 1.0 2.09 ± 0.08ab 0.24 ± 0.03bcd
23 2.5 1.5 1.73 ± 0.12bc 0.31 ± 0.03bcd
24 2.5 2.0 1.10 ± 0.12hi 0.21 ± 0.04cd
25 2.5 2.5 1.02 ± 0.03ij 0.13 ± 0.03d

Table 3: Effects of different concentrations and combinations of growth regulators on fresh weight of callus and anthocyanin induction of P. tunicoides.

Figure 2: Spectrogram for pigment extracting liquid of P. tunicoides callus.

Effects of illumination intensity for anthocyanins formation in callus

The callus of P. tunicoides was cultured on MS medium with optimum growth regulators combination (0.5 mg·L-1 6-BA and 1.5 mg·L-1 NAA) to induce anthocyanins, then combined with different illumination intensity treatment (light-dark cycle of 12 h). The results showed that Illumination is necessary for anthocyanins formation in callus (Figure 3). With the increase of illumination intensity, the anthocyanins content (Expressed in Abs. The same below) increased, the highest content at 2000 lx (Abs was 0.53), then decreased when up to an illumination intensity 2500 lx (Table 4). Some reports indicated that pigments production were greater in the light than in the dark [9], the reason is that the genes associated with anthocyanins biosynthesis could be activated by light irradiation [23], the expression of anthocyanins genes were regulated by UV-B receptors and were also stimulated by blue and red light [24,25] and signal transduction mechanisms as a role of complexity contacted with light-mediated control of anthocyanins gene expression [26]. In this way, a large of proteins that was an indication of increased gene expression would be produced by the red callus.

Figure 3: The effects of different illumination intensity to the callus anthocyanin of P. tunicoides (G: 0 lx; H: 500 lx; I: 1000 lx; J: 1500 lx; K: 2000 lx; L: 2500 lx). The effects of 2,4-D to antocyanins accumulation (M: added 2,4-D; N: no added 2,4-D).

Effects of 2,4-D for callus proliferation and anthocyanins accumulation

Under the above optimum conditions to induce anthocyanins of P. tunicoides (Including optimum combination of growth regulators and light intensity), adding 2,4-D (0, 0.5, 1.0, 1.5, 2.0 mg·L-1) to the media. The results reflected that the callus proliferated in varying degrees with the increase of 2,4-D concentration, and the anthocyanins content in callus decreased significantly (Table 4). In other words, 2,4-D strongly inhibited the accumulation of anthocyanins in callus (M and N in Figure 3). This may be due to the influence of 2,4-D as a suppressor to increase the incorporation of phenylalanine into amino acids, the products of phenylpropanoid metabolism were the precursors for anthocyanins biosynthesis, the phenylalanine was reduced by this conjugation reaction, and it was acted on by the enzymes of the phenylpropanoid pathway [27] is generally known that anthocyanins formation were controlled by anthocyanins genes that included structure genes (CHS, CHI, F3H, DFR) and regulatory genes (MYB10, bHLH3), 2,4-D inhibited the transcription of regulatory genes, the structure genes that were regulated by the regulatory genes also decreased. Therefore, the anthocyanins genes expression were inhibited by 2,4-D [15].

2, 4-D
(mg·L-1)
FW (g) Abs Illumination intensity
(lx)
FW (g) Abs
0.0 5.24 ± 0.09c 1.30 ± 0.02a 0 2.38 ± 0.07b 0.13 ± 0.05e
0.5 6.07 ± 0.06ab 0.08 ± 0.016b 500 3.17 ± 0.06a 0.23 ± 0.02de
1.0 6.60 ± 0.07a 0.04 ± 0.004b 1000 3.00 ± 0.10a 0.32 ± 0.02cd
1.5 5.96 ± 0.15b 0.07 ± 0.004b 1500 3.12 ± 0.08a 0.38 ± 0.03bc
2.0 5.90 ± 0.18b 0.04 ± 0.004b 2000 2.97 ± 0.10a 0.53 ± 0.03a
      2500 3.09 ± 0.09a 0.44 ± 0.02ab

Table 4: Effects of different concentrations of 2,4-D and illumination intensity on fresh weight of callus and anthocyanin accumulation of P. tunicoides.

According to our observation, the callus of P. tunicoides hardly grew in anthocyanins accumulation medium, and the callus became dead after produced anthocyanins. The direct cause behind this could be that anthocyanin belongs to the result of the secondary metabolism. During the process of secondary metabolites accumulation, the cell growth and production forming would be inhibited until the secondary metabolites to achieve the maximum, except the release of secondary metabolites or other regulate of artificial methods. End products caused the feedback inhibition of the first or the previous enzyme to result in the decrease of anthocyanins induction. Two reasons lead to plant cell could not growth normally, even dead between the slight toxicity and abound of end products.

Conclusion

Final conclusion, the present work demonstrated that the buds of P. tunicoides are suitable explants for inducing callus, the optimum medium is MS+0.5 mg·L-1 2,4-D+1.0 mg·L-1 6-BA+30 g·L-1 sucrose+7 g·L-1 agar. 0.5 mg·L-1 6-BA and 1.5 mg·L-1 NAA is the best combination for callus growth and anthocyanins formation. 2,4-D has a certain promoting effect for callus proliferation, but it strongly inhibits anthocyanin formation in callus. 2000 lx illumination intensity is the most favorable for anthocyanin synthesis in callus.

Conflict of Interest

This research belongs to the research project of the tutor, which is accomplished by the unified guidance of the tutor in the same laboratory. There is no conflict of interest. All the data and materials in this paper are reliable and available from our lab.

Acknowledgements

This research was funded to Ming-Sheng Zhang by a grant from the National Key Research and Development Project in China (No. 2016YFC050260403), the Major Special Project of Science and Technology Plan in Guizhou of China (No. 2017-5411-06 and 2017-5788), the Science and Technology Support Plan Project in Guizhou of China. (No. 2018-2797), the Special Fund of Science and Technology Innovation Talent Team Construction in Guizhou of China (No. 2016-5624), the Project of High-level Innovative Talents in Guizhou of China (No. 2015-4031), the Major Projects of Innovation Group in Guizhou of China (No. 2016-023) and the Modern Industrial Technical System Construction Project of Chinese Medicinal Materials in Guizhou of China (Grant No. GZCYTX-02).

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