LeSPL-CNR negatively regulates Cd acquisition through repressing nitrate reductase-mediated nitric oxide production in tomato
An SPL-type transcription factor, LeSPL-CNR, is negatively involved in NO production by modulating SlNR expression and nitrate reductase activity, which contributes to Cd tolerance.
Cadmium (Cd) is a highly toxic pollutant. Identifying factors affecting Cd accumulation in plants is a prerequisite for minimizing dietary uptake of Cd from crops grown with contaminated soil. Here, we report the involvement of a SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL) transcription factor LeSPL-CNR in Cd tolerance in tomato (Solanum lycopersicum). In comparison with the wild-type Ailsa Craig (AC) plants, the Colourless non-ripening (Cnr) epimutant displayed increased Cd accumulation and enhanced sensitivity to Cd, which was in well accordance with the repression of LeSPL-CNR expression. Cd stress-induced NO production was inhibited by nitrate reductase (NR) inhibitor, but not NO synthase-like enzyme inhibitor. Expression of LeSPL-CNR was negatively correlated with SlNR expression and the NR activity. We also demonstrated that LeSPL-CNR inhibited the SlNR promoter activity in vivo and bound to SlNR promoter sequence that does not contain a known SBP-binding motif. In addition, expression of an IRON-REGULATED TRANSPORTER1, SlIRT1, was more abundant in Cnr roots than AC roots under Cd stress. LeSPL-CNR may thus provide a molecular mechanism linking Cd stress response to regulation of NR-dependent NO production, which then contributes to Cd uptake via SlIRT1 expression in tomato.
KeywordsCadmium toxicity Iron uptake Solanum lycopersicum Transcription factor
- DAF-FM DA
Nitric oxide synthase
Solanum lycopersicum nitrate reductase
SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE
This work was supported financially by the Natural Science Foundation of China (31222049) and The Chang Jiang Scholars Program (JLY). We are grateful to Prof. Yiguo Hong (Hangzhou Normal University) for providing us the tomato seeds and his critical comments to the manuscript.
Compliance with ethical standards
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.
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