Cadmium decreases crown root number by decreasing endogenous nitric oxide, which is indispensable for crown root primordia initiation in rice seedlings.
Cadmium (Cd) is toxic to crown roots (CR), which are essential for maintaining normal growth and development in rice seedlings. Nitric oxide (NO) is an important signaling molecule that plays a pivotal role in plant root organogenesis. Here, the effects of Cd on endogenous NO content and root growth conditions were studied in rice seedlings. Results showed that similar to the NO scavenger, cPTIO, Cd significantly decreased endogenous NO content and CR number in rice seedlings, and these decreases were recoverable with the application of sodium nitroprusside (SNP, a NO donor). Microscopic analysis of root collars revealed that treatment with Cd and cPTIO inhibited CR primordia initiation. In contrast, although SNP partially recovered Cd-caused inhibition of CR elongation, treatment with cPTIO had no effect on CR elongation. L: -NMMA, a widely used nitric oxide synthase (NOS) inhibitor, decreased endogenous NO content and CR number significantly, while tungstate, a nitrate reductase (NR) inhibitor, had no effect on endogenous NO content and CR number. Moreover, enzyme activity assays indicated that treatment with SNP inhibited NOS activity significantly, but had no effect on NR activity. All these results support the conclusions that a critical endogenous NO concentration is indispensable for rice CR primordia initiation rather than elongation, NOS is the main source for endogenous NO generation, and Cd decreases CR number by inhibiting NOS activity and thus decreasing endogenous NO content in rice seedlings.
Xiong
Jie
J
State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, People's Republic of China.
Lu
Han
H
Lu
Kaixing
K
Duan
Yuxing
Y
An
Lingyao
L
Zhu
Cheng
C
D001565:Benzoates / Q000494:pharmacology; D002104:Cadmium / Q000633:toxicity*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D050901:Nitrate Reductase / Q000037:antagonists & inhibitors; D009569:Nitric Oxide / Q000378:metabolism* / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D012275:Oryza / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development*; D018517:Plant Roots / Q000033:anatomy & histology* / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D036226:Seedlings / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development*; D017973:Tungsten Compounds / Q000494:pharmacology; D019323:omega-N-Methylarginine / Q000494:pharmacology
D001565:Benzoates; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D007093:Imidazoles; D017973:Tungsten Compounds; D002104:Cadmium; C079393:1,3-dihydroxy-4,4,5,5-tetramethyl-2-(4-carboxyphenyl)tetrahydroimidazole; D009599:Nitroprusside; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D050901:Nitrate Reductase; C045951:tungstate