AI Article Synopsis
- Light affecting seed phytochromes in Arabidopsis thaliana influences ABA and GA signaling via a transcription factor called PIL5, with a newly identified mutant, somnus (som), that germinates in darkness.
- The som mutant shows decreased ABA and increased GA levels due to changes in hormone metabolic genes, but it doesn't affect the expression of key GA signaling components like RGA/RGA1.
- PIL5 activates SOM by binding to its promoter, indicating that SOM is part of the signaling pathway that regulates hormone metabolism during seed germination, especially under light conditions.
Article Abstract
Light absorbed by seed phytochromes of Arabidopsis thaliana modulates abscisic acid (ABA) and gibberellic acid (GA) signaling pathways at least partly via PHYTOCHROME-INTERACTING FACTOR3-LIKE5 (PIL5), a phytochrome-interacting basic helix-loop-helix transcription factor. Here, we report a new mutant, somnus (som), that germinates in darkness, independently of various light regimens. SOM encodes a nucleus-localized CCCH-type zinc finger protein. The som mutant has lower levels of ABA and elevated levels of GA due to expressional changes in ABA and GA metabolic genes. Unlike PIL5, however, SOM does not regulate the expression of GA-INSENSITIVE and REPRESSOR OF GA1 (RGA/RGA1), two DELLA genes encoding GA negative signaling components. Our in vivo analysis shows that PIL5 activates the expression of SOM by binding directly to its promoter, suggesting that PIL5 regulates ABA and GA metabolic genes partly through SOM. In agreement with these results, we also observed that the reduced germination frequency of a PIL5 overexpression line is rescued by the som mutation and that this rescue is accompanied by expressional changes in ABA and GA metabolic genes. Taken together, our results indicate that SOM is a component in the phytochrome signal transduction pathway that regulates hormone metabolic genes downstream of PIL5 during seed germination.
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|---|---|
| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2438461 | PMC |
| http://dx.doi.org/10.1105/tpc.108.058859 | DOI Listing |
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