Abstract
Background: 5-Aminolevunic acid (ALA), as a natural non-protein amino acid and the first essential precursor of tetrapyrrole biosynthesis in all living bodies, has been suggested to improve salt tolerance of plants. In the previous work, we reported that ALA induces H2O2 accumulation in roots of strawberry, which is involved in up-regulating Na+ transporter gene expressions to intercept Na+ in roots with less upward transport. However, the signal route is not clear.Results: In this study, we propose that nitric oxide (NO) is involved in ALA signaling cascade. Therefore, we applied sodium nitrosylpentacy (SNP, NO donor), Na2WO4 (NO biosynthetic inhibitor), and 2, 4-carboxyphenyl-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO, NO scavenger) to the culture solution when strawberry (Fragaria × ananassa Duch. cv. ‘Benihoppe’) was stressed by 100 mmol L-1 NaCl with or without exogenous ALA. The results reveal that salinity greatly impaired plant growth while 10 mg L-1 ALA or 10 µM SNP ameliorated the inhibition. When 5 µM Na2WO4 or cPTIO was co-treated, the ALA-improved salt tolerance was almost completely eliminated. This suggests that ALA-improved salt tolerance is dependent on NO presence. We found that salinity caused NO, H2O2, Na+ and Cl- increases in the whole plants, while ALA induced additional increases in roots but significant depressions in leaves. These tissue-specific responses to ALA are important for plant salt tolerance. Conclusion: We propose that the regulation of ALA in roots is critical, which is mediated through NO and then H2O2 signal to up-express genes related with Na+ and Cl- transport, selectively retaining Na+ and Cl- in roots with less upward transport. The hypothesis can reasonably explain how ALA-treated plants cope with toxic ions under salinity.
Patellin1 negatively regulates plant salt tolerance by attenuating nitric oxide accumulation in Arabidopsis
