doi: 10.5660/WTS.2020.9.4.369 Citation BibTeX RIS Mendeley

Low and High Levels of Exogenous 5-Aminolevulinic Acid Differentially Regulate Porphyrin Biosynthesis in Rice

• Jingil Kim
• Sunyo Jung

Rice plants were treated with either a low (50 μM, L-ALA) or a high (500 μM, H-ALA) concentration of 5-aminolevulinic acid (ALA) to find out the molecular mechanism underlying the ALA-caused modulation of porphyrin biosynthesis. Foliar application of H-ALA to rice plants developed necrotic symptom on leaves 2 days after the treatment, whereas no necrotic symptom was observed on leaves of L-ALA plants. After 2 days of ALA treatment, chlorophyll slightly increased in L-ALA plants, but decreased in H-ALA plants. While H-ALA treatment greatly decreased ALA-synthesizing capacity, L-ALA treatment did not show a significant change in ALA-synthesizing capacity. Plants treated with H-ALA exhibited a greater decline in transcript levels of HEMA1 than plants treated with L-ALA. The decrease in transcript levels of GSA did not differ between L-ALA and H-ALA plants, whereas ALAD greatly downregulated only in H-ALA plants. PPO1 was upregulated after 2 days of L-ALA treatment, but greatly downregulated with H-ALA treatment. Expression levels of CHLH, CHLD, and PORB remained or slightly decreased after 2 days of L-ALA treatment, but markedly decreased after 1 day of H-ALA treatment. This study demonstrates that a regulatory mechanism of porphyrin biosynthesis is differentially adjusted to the cellular demands in response to exogenous supply of low and high ALA concentrations.