Blue Light Mediates Chloroplast Avoidance and Enhances Photoprotection of Vanilla Orchid
Vanilla orchid, which is well-known for its flavor and fragrance, is cultivated in tropical and subtropical regions. This shade-loving plant is very sensitive to high irradiance. In this study, we show that vanilla chloroplasts started to have avoidance movement when blue light (BL) was higher than...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2020-10-01
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| Series: | International Journal of Molecular Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1422-0067/21/21/8022 |
| Summary: | Vanilla orchid, which is well-known for its flavor and fragrance, is cultivated in tropical and subtropical regions. This shade-loving plant is very sensitive to high irradiance. In this study, we show that vanilla chloroplasts started to have avoidance movement when blue light (BL) was higher than 20 μmol m<sup>−2</sup>s<sup>−1</sup> and significant avoidance movement was observed under BL irradiation at 100 μmol m<sup>−2</sup>s<sup>−1</sup> (BL100). The light response curve indicated that when vanilla was exposed to 1000 μmol m<sup>−2</sup>s<sup>−1</sup>, the electron transport rate (ETR) and photochemical quenching of fluorescence (qP) were significantly reduced to a negligible amount. We found that if a vanilla orchid was irradiated with BL100 for 12 days, it acquired BL-acclimation. Chloroplasts moved to the side of cells in order to reduce light-harvesting antenna size, and chloroplast photodamage was eliminated. Therefore, BL-acclimation enhanced vanilla orchid growth and tolerance to moderate (500 μmol m<sup>−2</sup>s<sup>−1</sup>) and high light (1000 μmol m<sup>−2</sup>s<sup>−1</sup>) stress conditions. It was found that under high irradiation, BL-acclimatized vanilla maintained higher ETR and qP capacity than the control without BL-acclimation. BL-acclimation induced antioxidant enzyme activities, reduced ROS accumulation, and accumulated more carbohydrates. Moreover, BL-acclimatized orchids upregulated photosystem-II-associated marker genes (<i>D1</i> and <i>PetC</i>), <i>Rubisco</i> and <i>PEPC</i> transcripts and sustained expression levels thereof, and also maximized the photosynthesis rate. Consequently, BL-acclimatized orchids had higher biomass. In short, this study found that acclimating vanilla orchid with BL before transplantation to the field might eliminate photoinhibition and enhance vanilla growth and production. |
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| ISSN: | 1661-6596 1422-0067 |