Regulation and Application of Aminolevulinic Acid (ALA) in Green Agroforestry

A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Ecophysiology and Biology".

Deadline for manuscript submissions: closed (27 March 2024) | Viewed by 9389

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Guest Editor
College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China
Interests: plant growth regulation; photosynthesis; stress tolerance; secondary metabolism; yield and quality; carbon peaking and carbon neutralization

Special Issue Information

Dear Colleagues,

Background and history of this topic: 5-Aminolevulinic acid (ALA) is a natural δ-amino acid which does not participate in protein biosynthesis. As an essential biosynthetic precursor of all tetrapyrrole compounds, such as chlorophylls, hemes, and phytochromes, it exhibits a great regulatory function in plant growth and development, as well as in environmental adaptation. ALA can be synthesized chemically or biosynthesized by microorganism fermatation, and has been suggested to have huge potential and broad prospects when applied in agronomy, horticulture, and forestry as an insectcide, a fungicide, an herbcide, a colourant, or a growth regulator.  

Aim and scope of the Special Issue: In this Special Issue, we will focus on ALA's own biosynthesis and metabolism, the new mechanisms of ALA in regulating plant growth, and the new application of ALA in green agroforestry production. Any achievements, including new materials, new technologies, new methods, and new applications related to ALA, are within the scope of our concern. The aim is to concentratedly display ALA research for the first time, informing more people about ALA and potentially increasing the attention around it. We also hope that ALA can play a greater role in agriculture and forestry through yield increase, stress resistance, quality improvement, and efficiency promotion, especially in the practise of carbon peak and carbon neutrality.

Cutting-edge research topics: highly efficient production of ALA; molecular mechanisms of ALA regulating the plant biological process; new bioregulatory functions of ALA; cross-talk of ALA with classic plant hormones.

What kind of papers we are soliciting: reseach articles; mini reviews; methodologies; etc.

Prof. Dr. Liangju Wang
Guest Editor

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Keywords

  • agroforestry
  • ALA
  • biosynthesis
  • photosynthesis
  • plant growth regulation
  • plant hormones
  • production
  • quality
  • stress resistance

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Published Papers (5 papers)

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Research

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20 pages, 4170 KiB  
Article
Exogenous 5-Aminolevulinic Acid Promotes Osmotic Stress Tolerance of Walnuts by Modulating Photosynthesis, Osmotic Adjustment and Antioxidant Systems
by Yan Zhong, Changzhou Liu, Bo Wei, Jianting Zhang, Yuyan An and Liangju Wang
Forests 2023, 14(9), 1789; https://doi.org/10.3390/f14091789 - 1 Sep 2023
Cited by 6 | Viewed by 1329
Abstract
The walnut (Juglans regia L.) is an important economic tree worldwide, often cultivated in arid and semiarid regions. Improving the drought tolerance is of significance for walnut growth, production, and economic effectiveness. 5-Aminolevulinic acid (ALA) is a novel plant growth regulator which [...] Read more.
The walnut (Juglans regia L.) is an important economic tree worldwide, often cultivated in arid and semiarid regions. Improving the drought tolerance is of significance for walnut growth, production, and economic effectiveness. 5-Aminolevulinic acid (ALA) is a novel plant growth regulator which raises plant tolerance to various stressful conditions. Here, foliage application of ALA was carried out to uncover its effect on walnuts under polyethylene glycol (PEG) 6000-stimulated osmotic stress. Our results displayed that exogenous ALA greatly promoted the chlorophyll content, photochemical activities, and gas exchange in walnuts under osmotic stress. ALA led to a considerable accumulation of compatible osmotic solutes, enabling walnuts to maintain osmotic equilibrium against drought stress. Furthermore, ALA alleviated the reactive oxygen species (ROS) damages on osmotically stressed walnuts through enhancing the antioxidant enzyme activities, as well as decreasing the ROS and malondialdehyde (MDA) content. The relative water content (RWC) in the ALA-treated leaves was higher than that of PEG-stressed, while the RWC in the substrate of ALA treatment was significantly lower than that of the PEG-stressed, further suggesting that ALA promotes plant water uptake from the substrate under osmotic stress. These demonstrate that ALA improves the photosynthesis, osmotic adjustment, antioxidant systems and, consequently, the walnuts’ drought tolerance. Full article
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18 pages, 8512 KiB  
Article
Effects of Exogenous ALA on Leaf Photosynthesis, Photosynthate Transport, and Sugar Accumulation in Prunus persica L.
by Ruolin Liang, Liangju Wang, Xinqing Wang, Jianting Zhang and Xing Gan
Forests 2023, 14(4), 723; https://doi.org/10.3390/f14040723 - 31 Mar 2023
Cited by 8 | Viewed by 1826
Abstract
Peaches/nectarines (Prunus persica L.) are widely cultivated worldwide. As with other species, the sugar content is the most important trait for fruit quality, especially for precocious cultivars. Most fruits need to improve their sugar content in order to be more profitable under [...] Read more.
Peaches/nectarines (Prunus persica L.) are widely cultivated worldwide. As with other species, the sugar content is the most important trait for fruit quality, especially for precocious cultivars. Most fruits need to improve their sugar content in order to be more profitable under fierce market competition. 5-Aminolevulinic acid (ALA), a naturally occurring δ-amino acid, has been shown to improve leaf photosynthesis and fruit quality, especially sugar content. However, the mechanisms are not clear. The objective of this study is to determine the effects of exogenous ALA on leaf photosynthesis, assimilate transport, and sugar accumulation during fruit development. We used the field-cultivated precocious nectarine ‘Zhongyoutao 4’ and potted cultivated peach ‘Zhongai 33’ as materials, whereas in the second experiment, we used 14C radiolabeling to trace 14C fixation in leaves, transport in branches, and distribution in different organs. The results showed that ALA significantly enhanced the photosynthetic gas exchange capacity, and the effects were maintained for at least one month. The results of the 14C radiolabel experiment showed that ALA enhanced 14C fixation in leaves, promoted the transport to fruits, and reduced the allocation rate of young leaves. This suggests that ALA enlarges “source” volume and strengthens “sink” competition; therefore, assimilate translocation to fruits is promoted. It was observed that sucrose contributed the main saccharide for peach fruit quality at maturity, which might not be converted from glucose or fructose but from starch degradation. ALA improved starch accumulation in the young fruits as well as degradation during maturity. The RT-qPCR showed that the expression of most genes involved in sugar metabolism did not correlate or even negatively correlate with fruit sucrose content. However, the expressions of SWEET1/6/7/8/15/16/17 were highly correlated with the sucrose content, and exogenous ALA treatment up-regulated the gene expression at fruit maturity, suggesting they might play an important role in fruit sugar accumulation. These results provide important theoretical support for ALA application in fruit quality improvement, as well as a regulatory mechanism study on sugar accumulation in fruits. Full article
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20 pages, 5671 KiB  
Article
Transcriptome Analysis of 5-Aminolevulinic Acid Contributing to Cold Tolerance in Tea Leaves (Camellia sinensis L.)
by Fei Yan, Dong Qu, Xiaohua Chen, Jianjun Yang, Haitao Zeng and Xinsheng Li
Forests 2023, 14(2), 198; https://doi.org/10.3390/f14020198 - 20 Jan 2023
Viewed by 2075
Abstract
Tea (Camellia sinensis L.) is an important perennial cash crop and a typical subtropical plant. It is widely concerned because of its unique flavor and health benefits. In recent years, low temperatures have severely restricted the growth of tea plants and quality [...] Read more.
Tea (Camellia sinensis L.) is an important perennial cash crop and a typical subtropical plant. It is widely concerned because of its unique flavor and health benefits. In recent years, low temperatures have severely restricted the growth of tea plants and quality of tea products, especially in spring. As a common precursor for all porphyrin compounds, 5-aminolevulinic acid (ALA) is involved in photosynthesis and respiration and plays an active role in improving salt, drought and low-temperature tolerance in plants. However, it is not yet clear what affect exogenous ALA has on tea plants’ tolerance under low temperature. In the present study, we collected and deciphered the transcriptome profiles from Shaancha No. 1 leaf tissues under low temperature (−4 °C) treatment (T-4), exogenous ALA application (T-A), pretreated ALA before low temperature (T-A-4) and untreated control (T-CK). Results showed that 4990 (2375 up- and 2615 down-regulated), 223 (103 up- and 120 down-regulated) and 92 (13 up- and 79 down-regulated) differentially expression genes (DEGs) were identified at T-CK vs. T-4, T-CK vs. T-A and T-4 vs. T-A-4, respectively. Both T-4 and T-A treatments triggered a myriad of stress resistance genes up-regulated related to multiple signaling pathways by means of Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. This included MAPK, a toll-like receptor that signals pathways involved in cold resistance. However, gene ontology (GO) analysis showed that the DEGs in T-4 treatment were mainly enriched in the phenylpropanoid metabolic and redox processes that were relevant to membrane structure damage response. In contrast, the DEGs in T-A treatment were mainly enriched in cell recognition and amylase activity. Furthermore, in pairwise comparison of T-A-4 vs. T-4, the DEGs were enriched in ascorbate and aldarate, retionol, taurine and hypotaurine, glutathione metabolic pathways and two biosynthesis process including zeatin, diterpenoid biosynthesis, which might contribute to mitigating the damage caused by low temperature. Overall, these results indicated that exogenous ALA application may improve the biochemical attributes and enhance the tolerance to low temperature, which provides a valuable strategy to improve tea quality and cold stress. Full article
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14 pages, 2161 KiB  
Article
Analysis of the Alternative Splicing Events of Exogenous δ-Aminolevulinic Acid under NaCl Stress in Wild Jujube Seedlings
by Chunmei Zhu, Zhiyu Liu, Xinyi Chang, Zhijun Zhang, Wenchao Shi, Zhongrong Zhang, Baolong Zhao and Junli Sun
Forests 2022, 13(12), 2076; https://doi.org/10.3390/f13122076 - 6 Dec 2022
Cited by 3 | Viewed by 1399
Abstract
Salt injury, as an abiotic stress factor, seriously affects the quality and yield of crops. This study was conducted by analyzing alternative splicing in the control (CK), δ-aminolevulinic acid (ALA), NaCl, and ALA + NaCl treatments of wild jujube (Zizyphus spinosus (Bunge)Hu) using [...] Read more.
Salt injury, as an abiotic stress factor, seriously affects the quality and yield of crops. This study was conducted by analyzing alternative splicing in the control (CK), δ-aminolevulinic acid (ALA), NaCl, and ALA + NaCl treatments of wild jujube (Zizyphus spinosus (Bunge)Hu) using RNA-seq. It was found that the unique differential alternative splicing is closely related to the alleviation of salt stress and the analyzed intermediates of chlorophyll synthesis and chlorophyll content in the leaves. The results showed that the content and synthesis of chlorophyll were reduced and disrupted in wild jujube leaves under NaCl stress, and the exogenous spraying of ALA could alleviate the effect of NaCl stress on the content of chlorophyll. RNA-seq indicated that the alternative splicing of genes was dominated by exon skipping in all the experimental treatments. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed that the CK and ALA + NaCl comparison groups were primarily enriched in porphyrin and chlorophyll metabolism, chloroplast, and energy metabolism pathways. It is hypothesized that ALA treatment can alleviate the effects of salt stress on chlorophyll by altering the alternative splicing of genes related to photosynthesis, chlorophyll metabolism, and energy metabolism in wild jujube. In addition, the verification of alternative splicing genes related to chlorophyll metabolism in wild jujube revealed that treatment with ALA significantly upregulated the expression of HEMH, UROIII, and ChlD genes in the leaves under salt stress and increased the content of the chlorophyll biosynthetic intermediates endogenous ALA, porphobilinogen, protoporphyrin IX, Mg-protoporphyrin IX, and protochlorophyllide, which served to alleviate the effects of NaCl stress on chlorophyll in wild jujube. Full article
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Review

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33 pages, 2573 KiB  
Review
Regulation of 5-Aminolevunilic Acid and Its Application in Agroforestry
by Liangju Wang, Jianting Zhang, Yan Zhong, Liuzi Zhang, Hao Yang, Longbo Liu, Jiayi Zhou, Malik Mohsin Iqbal and Xing Gan
Forests 2023, 14(9), 1857; https://doi.org/10.3390/f14091857 - 12 Sep 2023
Cited by 5 | Viewed by 2123
Abstract
The review briefly introduces the natural occurrence, physicochemical properties, and biosynthesis of 5-aminolevuinic acid (ALA) and highlights a variety of applications in the planting industry and its possible mechanisms. It has been known that ALA can be used as biological pesticides, fungicides, and [...] Read more.
The review briefly introduces the natural occurrence, physicochemical properties, and biosynthesis of 5-aminolevuinic acid (ALA) and highlights a variety of applications in the planting industry and its possible mechanisms. It has been known that ALA can be used as biological pesticides, fungicides, and herbicides when the concentrations are higher than 838 mg L−1 (about 5 mmol L−1). When ALA concentrations are 100–300 mg L−1, it can be used to thin surplus flowers in the spring of orchards and promote fruit coloration before maturation. When the concentrations are lower than 100 mg L−1, especially not higher than 10 mg L−1, ALA can be used as a new plant growth regulator to promote seed germination, plant (including root and shoot) growth, enhance stress tolerance, increase crop yield, and improve product quality. In photosynthesis, ALA is involved in the regulation of the whole process. In stress tolerance, ALA induces plant preventive and protective systems through the NO/H2O2 signaling network. In secondary metabolism, ALA regulates many gene expressions encoding transcription factors or function proteins to promote anthocyanin and flavonol biosynthesis and accumulation. In general, ALA promotes plant health and robustness, reduces the use of chemical fertilizers and pesticides—which is conducive to improving the ecological environment, human production, and living conditions—and has a broad application prospect in agroforestry production. As a new plant growth regulator with multiple and powerful functions, the underlying regulatory mechanisms need more study. Full article
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