Mechanism Enhancing Arabidopsis Resistance to Cadmium: The Role of NRT1.5 and Proton Pump

• Published in: Frontiers in plant science Vol. 9; p. 1892
• Main Authors: Wang, Tao, Hua, Yingpeng, Chen, Moxian, Zhang, Jianhua, Guan, Chunyun, Zhang, Zhenhua
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 19-12-2018
• Subjects: ABA signaling; Cd stress; NO3; NRT1.5; NRT1.8; Plant Science; proton pump activity; ABA signaling; Cd stress; proton pump activity; NO3; NRT1.5; NRT1.8
• ISSN: 1664-462X; 1664-462X
• DOI: 10.3389/fpls.2018.01892

Heavy metal pollution is serious in China, and abscisic acid (ABA) is an important stress hormone. How it regulates plant tolerance to cadmium remains unclear, so we aimed to explore the molecular mechanism responsible for enhanced cadmium resistance in Arabidopsis wild-type and mutant plants and
seedlings.
Arabidopsis/
were cultured hydroponically for 28/15 days and then treated with 20/10 μM Cd/Cd+ABA (5 μM) for 3/4 days. Chlorophyll degradation rate, SPAD values, proline, MDA, ABA,
, and Cd concentrations were measured in root vacuoles and protoplasts; root to shoot
and Cd concentration ratios were determined and
, and
related gene expression was studied.
Cytoplasmic ABA levels in root cells of
and
Arabidopsis mutants were significantly lower than those in the wild-type, apparently making the latter more resistant to Cd.
long-distance transporter
responded to ABA signaling by downregulating its own expression, while
did not respond. Concomitantly, proton pump activity in wild-type plants was higher than in the
and
mutants; thus, more
and Cd accumulated in the vacuoles of wild-type root cells. ABA application inhibited Cd absorption by
.
responded to exogenous ABA signal by downregulating its own expression, while the lack of response by
resulted in increased amount of
accumulating in the roots to participate in the anti-cadmium reaction.
responds to the ABA signal to inhibit its own expression, whereas unresponsiveness of
causes accumulation of
in the roots; thus, enhancing Cd resistance. In Arabidopsis, because of proton pump action, more
and Cd accumulate in the vacuoles of Arabidopsis root cells, thereby reducing damage by Cd toxicity. However, in
, the addition of exogenous ABA inhibited Cd absorption. Our data provide a sound basis to the theoretical molecular mechanism involved in hormone signaling during response of plants to heavy metal stress.