Heping Cao
Wenfang Gong
Jun Rong
Deyi Yuan- 1United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
- 2Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees, Central South University of Forestry and Technology, Changsha, China
- 3School of Life Sciences, Nanchang University, Nanchang, China
Editorial on the Research Topic
Woody oil crops: key trait formation and regulation
Woody oil crops are renewable forest resources to produce high-quality oils for food, feed and industrial uses. They contain diverse fatty acids and valuable nutritional components. They can be edible and/or industrial crops (Table 1). Edible woody oil crops include cocoa (Medeiros de Azevedo et al., 2020), coconut (Deen et al., 2021), hazelnut (Crews et al., 2005), idesia (Zhang et al., 2023), maple (Song et al., 2022), oil palm (Mancini et al., 2015), oil olive (Battino et al., 2019), pecan (Scapinello et al., 2017), peony (Yang et al., 2017), pine (Zeng et al., 2012), yellow horn (Liang et al., 2021; Zang et al., 2021), oil-tea camellia (Zeng et al., 2014; Luan et al., 2020; Li et al., 2022; Song et al., 2023) and walnut (Rébufa et al., 2022). Industrial woody oil crops include castor (Román-Figueroa et al., 2020), camelina (Berti et al., 2016), crambe (Lalas et al., 2012), flax (Goyal et al., 2014) and Tung (Dyer et al., 2002; Shockey et al., 2006; Cao et al., 2013; Zhang et al., 2014; Li et al., 2017; Liu et al., 2019; Zhang et al., 2019). Many woody oil crops have special fatty acid composition (Table 1). Key traits of woody oil crops are essential for breeding and production, such as fruit/seed yield, size, weight, oil content, fatty acid and other valuable compositions, tolerance to drought, cold, and low nutrition stresses. Compared to herbaceous oil crops, key trait formation and regulation in woody oil crops are not well studied.
Table 1 Woody oil crops and their oil content and major oil composition.
This Research Topic is aimed to summarize recent advances in key trait formation and regulation in woody oil crops for facilitating breeding and production. Thirteen articles have been published including 12 original research articles and one review article. Among them, ten papers focus on Camellia oleifera, and one each on Pinus koraiensis, Paeonia ostii and Carya cathayensis.
Genome and genetic diversity
Camellia oleifera genome is very complex. One article reviewed the “Genomic and genetic advances of oiltea-camellia (Camellia oleifera)” (Ye et al.). The report summarized the recent assembly of the reference genomes and identified putative genes related to economic traits, disease resistance and environmental stress tolerances. To explore the genetic diversity of wild C. oleifera phenotypic traits, another article reported “Characterization and comprehensive evaluation of phenotypic characters in wild Camellia oleifera germplasm for conservation and breeding” (Chen et al.). They used 143 wild C. oleifera germplasm resources and identified 41 characters based on the quantization of physical and chemical descriptors and digital image analysis.
Flower bud formation
The number of flower buds is a main factor affecting the crop yield. One investigation studied “Co-regulatory effects of hormone and mRNA–miRNA module on flower bud formation of Camellia oleifera” (Du et al.). The results showed that GA3, ABA, tZ, JA, and SA contents in the buds were higher than those in the fruit and that differentially expressed genes were notably enriched in hormone signal transduction and the circadian system.
Oil accumulation
Camellia oleifera oil quality is mainly determined by linoleic acid (LA) and α-linolenic acid (ALA) content. One study reported “Enhancing the accumulation of linoleic acid and α-linolenic acid through the pre-harvest ethylene treatment in Camellia oleifera” (Li et al.). The study confirms the role of ethylene in LA and ALA regulation and provides new insights into the potential utilization of ethylene as a LA and ALA inducer.
Nutrient deficiency
Phosphorus deficiency in the acidic soil poses severe challenges for the growth and productivity. WRKY transcription factors play important roles in plant responses to biotic/abiotic stresses. One article reported “Genome-wide identification of the WRKY gene family in Camellia oleifera and expression analysis under phosphorus deficiency” (Su et al.). The authors identified 89 WRKY proteins into three groups, detected WRKY variants and mutations, and suggested that WRKYs play a crucial role in the transportation and recycling phosphate in leaves.
Cold and drought stresses
The molecular mechanisms of freezing tolerance are unresolved in perennial trees. One investigation found that “Field plus lab experiments help identify freezing tolerance and associated genes in subtropical evergreen broadleaf trees: A case study of Camellia oleifera” (Xie et al.). Combing transcriptome results from the field and lab experiments, the common genes associated with freezing-stress responses were identified. Drought stress is another major obstacle in C. oleifera planting industry. The other investigation reported that “Integration of mRNA and miRNA analysis reveals the differentially regulatory network in two different Camellia oleifera cultivars under drought stress” (He et al.). Their research improves the understanding of the regulatory network response to drought stress and variety-specific responses improving drought tolerance.
Grafting
Camellia oleifera scion significantly affects the rootstock properties after grafting and impacts the grafted seedling growth. One study reported “Untargeted metabolism approach reveals difference of varieties of bud and relation among characteristics of grafting seedlings in Camellia oleifera” (Long et al.). They detected 554 metabolites significantly different among four varieties and 29 metabolic pathways significantly changed by metabolomics analysis.
Disease resistance
Anthracnose outbreak severely affects oil tea camellia production in China. One paper revealed that “Overexpression of dihydroflavonol 4-reductase (CoDFR) boosts flavonoid production involved in the anthracnose resistance” (Yang et al.). The results showed that CoDFR may play an important role in flavonoid-mediated defense mechanisms during anthracnose invasion in resistant C. oleifera. WRKY transcription factor family members are vital regulators in plant response to pathogen infection. Another paper reported “Identification of Camellia oleifera WRKY transcription factor genes and functional characterization of CoWRKY78” (Li et al.). They identified 90 WRKY members, verified the expression patterns between anthracnose-resistant and -susceptible cultivars, and demonstrated that multiple candidate CoWRKYs can be induced by anthracnose.
Oil synthesis gene
Chinese hickory (Carya cathayensis) produces nuts with high-quality edible oils rich in oleic acid. Stearoyl-ACP desaturase (SAD) plays an important role in oleic acid accumulation by catalyzing the first step converting stearic acid to oleic acid. One paper reported the “Analysis of Delta(9) fatty acid desaturase gene family and their role in oleic acid accumulation in Carya cathayensis kernel” (Si et al.). The study identified five members of SAD genes, isolated the full-length cDNAs, analyzed their expression, located them in the chloroplast, and studied their function in Saccharomyces cerevisiae, Nicotiana benthamiana, and walnut.
N and P nutrients
Pine (Pinus koraiensis) produces high-quality timber and high value health-care nut oil. One article reported that “Large investment of stored nitrogen and phosphorus in female cones is consistent with infrequent reproduction events of Pinus koraiensis, a high value woody oil crop in Northeast Asia” (Wu et al.). High nutrient sink strength of cones and vegetative tissues of reproductive branches suggested that customized fertilization practices can help improve crop yield in Pinus koraiensis.
Non-structural carbohydrates
Non-structural carbohydrates (NSC) play important roles in energy supply for normal growth and reproduction under environmental stress. One article described the “Effects of NSC in different organs and at different growth stages on the yield of oil peony Fengdan with different ages” (Wang et al.). Results showed that the biomass, yield (seed biomass), soluble sugars, starch, and NSC reserve at the whole tree level increased with the increase in age. NSC level, particularly the concentration of soluble sugars in stems mainly influences Fengdan yield.
Author contributions
HC: Writing – original draft, Writing – review & editing, Conceptualization, Project administration. WG: Writing – original draft. JR: Writing – review & editing. DY: Writing – review & editing.
Funding
The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was supported by the USDA-ARS Quality and Utilization of Agricultural Products National Program 306 through ARS Research Projects 6054-41000-103-00-D and 6054-41000-113-00-D. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. USDA is an equal opportunity provider and employer. This work was also supported by the Science and Technology Innovation Program of Hunan Province (2022RC1152) and the National Key R&D Program of China (2018YFD1000603-1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Acknowledgments
We thank the authors for their valuable contributions and the referees for their rigorous reviews.
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Publisher’s note
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References
Battino, M., Forbes-Hernandez, T. Y., Gasparrini, M., Afrin, S., Cianciosi, D., Zhang, J., et al. (2019). Relevance of functional foods in the Mediterranean diet: the role of olive oil, berries and honey in the prevention of cancer and cardiovascular diseases. Crit. Rev. Food Sci. Nutr. 59 (6), 893–920. doi: 10.1080/10408398.2018.1526165
Berti, M., Gesch, R., Eynck, C., Anderson, J., Cermak, S. (2016). Camelina uses, genetics, genomics, production, and management. Ind. Crops Products 94, 690–710. doi: 10.1016/j.indcrop.2016.09.034
Cao, H., Shockey, J. M., Klasson, K. T., Mason, C. B., Scheffler, B. E. (2013). Developmental regulation of diacylglycerol acyltransferase family gene expression in tung tree tissues. PloS One 8 (10), e76946. doi: 10.1371/journal.pone.0076946
Crews, C., Hough, P., Godward, J., Brereton, P., Lees, M., Guiet, S., et al. (2005). Study of the main constituents of some authentic hazelnut oils. J. Agric. Food Chem. 53 (12), 4843–4852. doi: 10.1021/jf047836w
Deen, A., Visvanathan, R., Wickramarachchi, D., Marikkar, N., Nammi, S., Jayawardana, B. C., et al. (2021). Chemical composition and health benefits of coconut oil: an overview. J. Sci. Food Agric. 101 (6), 2182–2193. doi: 10.1002/jsfa.10870
Dyer, J. M., Chapital, D. C., Kuan, J. C., Mullen, R. T., Turner, C., McKeon, T. A., et al. (2002). Molecular analysis of a bifunctional fatty acid conjugase/desaturase from tung. Implications for the evolution of plant fatty acid diversity. Plant Physiol. 130 (4), 2027–2038. doi: 10.1104/pp.102.010835
Goyal, A., Sharma, V., Upadhyay, N., Gill, S., Sihag, M. (2014). Flax and flaxseed oil: an ancient medicine & modern functional food. J. Food Sci. Tech Mys 51 (9), 1633–1653. doi: 10.1007/s13197-013-1247-9
Lalas, S., Gortzi, O., Athanasiadis, V., Dourtoglou, E., Dourtoglou, V. (2012). Full characterisation of hochst. Seed oil. J. Am. Oil Chem. Soc. 89 (12), 2253–2258. doi: 10.1007/s11746-012-2122-y
Li, C., Long, Y., Lu, M., Zhou, J., Wang, S., Xu, Y., et al. (2022). Gene coexpression analysis reveals key pathways and hub genes related to late-acting self-incompatibility in Camellia oleifera. Front. Plant Sci. 13. doi: 10.3389/fpls.2022.1065872
Li, Z., Long, H., Zhang, L., Liu, Z., Cao, H., Shi, M., et al. (2017). The complete chloroplast genome sequence of tung tree (Vernicia fordii): Organization and phylogenetic relationships with other angiosperms. SciRep 7 (1), 1869. doi: 10.1038/s41598-017-02076-6
Liang, Q., Fang, H. C., Liu, J. N., Zhang, B. H., Bao, Y., Hou, W. R., et al. (2021). Analysis of the nutritional components in the kernels of yellowhorn ((Xanthoceras sorbifolium Bunge) accessions. J. Food Compos Anal. 100, (103925). doi: 10.1016/j.jfca.2021.103925
Liu, M., Long, H., Li, W., Shi, M., Cao, H., Zhang, L., et al. (2019). Boosting C16 fatty acid biosynthesis of Escherichia coli, yeast and tobacco by tung tree (Vernicia fordii Hemsl.) beta-hydroxyacyl-acyl carrier protein dehydratase gene. Ind. Crops Products 127, 46–54. doi: 10.1016/j.indcrop.2018.10.067
Luan, F., Zeng, J. S., Yang, Y., He, X. R., Wang, B. J., Gao, Y. B., et al. (2020). Recent advances in Camellia oleifera Abel: A review of nutritional constituents, biofunctional properties, and potential industrial applications. J. Funct. Foods 75 (104242), 104242. doi: 10.1016/j.jff.2020.104242
Mancini, A., Imperlini, E., Nigro, E., Montagnese, C., Daniele, A., Orru, S., et al. (2015). Biological and nutritional properties of palm oil and palmitic acid: effects on health. Molecules 20 (9), 17339–17361. doi: 10.3390/molecules200917339
Medeiros de Azevedo, W., Ferreira Ribeiro de Oliveira, L., Alves Alcantara, M., Tribuzy de Magalhaes Cordeiro, A. M., Florentino da Silva Chaves Damasceno, K. S., Kelly de Araujo, N., et al. (2020). Physicochemical characterization, fatty acid profile, antioxidant activity and antibacterial potential of cacay oil, coconut oil and cacay butter. PloS One 15 (4), e0232224. doi: 10.1371/journal.pone.0232224
Rébufa, C., Artaud, J., Le Dréau, Y. (2022). Walnut (Juglans regia L.) oil chemical composition depending on variety, locality, extraction process and storage conditions: A comprehensive review. J. Food Compos Anal. 110, (104534). doi: 10.1016/j.jfca.2022.104534
Román-Figueroa, C., Cea, M., Paneque, M., González, M. E. (2020). Oil content and fatty acid composition in castor bean naturalized accessions under mediterranean conditions in Chile. Agronomy-Basel 10 (8), 1145. doi: 10.3390/agronomy10081145
Scapinello, J., Magro, J. D., Block, J. M., Di Luccio, M., Tres, M. V., Oliveira, J. V. (2017). Fatty acid profile of pecan nut oils obtained from pressurized n-butane and cold pressing compared with commercial oils. J. Food Sci. Technol. 54 (10), 3366–3369. doi: 10.1007/s13197-017-2771-9
Shockey, J. M., Gidda, S. K., Chapital, D. C., Kuan, J. C., Dhanoa, P. K., Bland, J. M., et al. (2006). Tung tree DGAT1 and DGAT2 have nonredundant functions in triacylglycerol biosynthesis and are localized to different subdomains of the endoplasmic reticulum. Plant Cell 18 (9), 2294–2313. doi: 10.1105/tpc.106.043695
Song, Q., Gong, W., Yu, X., Ji, K., Jiang, Y., Chang, Y., et al. (2023). Transcriptome and anatomical comparisons reveal the effects of methyl jasmonate on the seed development of Camellia oleifera. J. Agric. Food Chem. 71 (17), 6747–6762. doi: 10.1021/acs.jafc.3c00059
Song, W., Zhang, K., Xue, T., Han, J., Peng, F., Ding, C., et al. (2022). Cognitive improvement effect of nervonic acid and essential fatty acids on rats ingesting Acer truncatum Bunge seed oil revealed by lipidomics approach. Food Funct. 13 (5), 2475–2490. doi: 10.1039/d1fo03671h
Yang, X., Zhang, D., Song, L. M., Xu, Q., Li, H., Xu, H. (2017). Chemical profile and antioxidant activity of the oil from peony seeds (Paeonia suffruticosa Andr.). Oxid. Med. Cell Longev 2017, 9164905. doi: 10.1155/2017/9164905
Zang, E., Qiu, B., Chen, N., Li, C., Liu, Q., Zhang, M., et al. (2021). Xanthoceras sorbifolium bunge: A review on botany, phytochemistry, pharmacology, and applications. Front. Pharmacol. 12. doi: 10.3389/fphar.2021.708549
Zeng, Y., Tan, X., Zhang, L., Jiang, N., Cao, H. (2014). Identification and expression of fructose-1,6-bisphosphate aldolase genes and their relations to oil content in developing seeds of tea oil tree (Camellia oleifera). PloS One 9 (9), e107422. doi: 10.1371/journal.pone.0107422
Zeng, W. C., Zhang, Z., Gao, H., Jia, L. R., He, Q. (2012). Chemical composition, antioxidant, and antimicrobial activities of essential oil from pine needle (Cedrus deodara). J. Food Sci. 77 (7), C824–C829. doi: 10.1111/j.1750-3841.2012.02767.x
Zhang, L., Jia, B., Tan, X., Thammina, C. S., Long, H., Liu, M., et al. (2014). Fatty acid profile and unigene-derived simple sequence repeat markers in tung tree (Vernicia fordii). PloS One 9 (8), e105298. doi: 10.1371/journal.pone.0105298
Zhang, L., Liu, M., Long, H., Dong, W., Pasha, A., Esteban, E., et al. (2019). Tung tree (Vernicia fordii) genome provides A resource for understanding genome evolution and improved oil production. Genomics Proteomics Bioinf. 17 (6), 558–575. doi: 10.1016/j.gpb.2019.03.006
Keywords: woody oil crops, trait formation, molecular mechanisms, regulation, oil content (OC) and fatty acid composition
Citation: Cao H, Gong W, Rong J and Yuan D (2023) Editorial: Woody oil crops: key trait formation and regulation. Front. Plant Sci. 14:1328990. doi: 10.3389/fpls.2023.1328990
Received: 27 October 2023; Accepted: 06 November 2023;
Published: 10 November 2023.
Edited and Reviewed by:
Leo Marcelis, Wageningen University and Research, NetherlandsCopyright © 2023 Cao, Gong, Rong and Yuan. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Heping Cao, SGVwaW5nLkNhb0B1c2RhLmdvdg==