Nitric oxide signaling is involved in the response to iron deficiency in the woody plant Malus xiaojinensis.
To cope with iron (Fe) deficiency, plants have evolved a wide range of adaptive responses from changes in morphology to altered physiological responses. Recent studies have demonstrated that nitric oxide (NO) is involved in the Fe-deficiency response through hormonal signaling pathways. Here, we report that NO plays a significant role in Malus xiaojinensis, an Fe-efficient woody plant. Fe deficiency triggered significant accumulation of NO in the root system, predominantly in the outer cortical and epidermal cells of the elongation zone. The NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO) completely arrested Fe deficiency-induced root hair formation, blocked the increase in root ferric-chelate reductase activity and in root H+excretion, further reduced the active iron content in young leaves and roots, and prevented the upregulation of the critical Fe-related genes, FIT, MxFRO2-like, and MxIRT1. These conditions were restored under Fe deficiency by treatment with the NO donor, sodium nitroprusside (SNP). Additionally, chlorophyll content and relative expression levels of the genes chlorophyll a deoxygenase (MxCAO) and polyamine oxidase (MxPAO) were not changed significantly following Fe deficiency for 6 d; however, SNP treatment increased MxHEMA gene expression. Interestingly, the Fv/Fm ratio, the maximum quantum yield of photosystem II (PSII), decreased significantly following cPTIO treatment. We observed more severe chlorosis under Fe deficiency with cPTIO treatment for 9 d. These results strongly suggest that NO mediates a range of responses to Fe deficiency in M. xiaojinensis, from morphological changes to the regulation of physiological processes and gene expression.
Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China; Institute for Horticultural Plants, China Agricultural University, Beijing, 100193, China.
Longmei
L
Zhai
Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China; Institute for Horticultural Plants, China Agricultural University, Beijing, 100193, China.
Dashuang
D
Xiao
Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China; Institute for Horticultural Plants, China Agricultural University, Beijing, 100193, China.
Chaohua
C
Sun
Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China; Institute for Horticultural Plants, China Agricultural University, Beijing, 100193, China.
Ting
T
Wu
Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China; Institute for Horticultural Plants, China Agricultural University, Beijing, 100193, China.
Zhenhai
Z
Han
Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China; Institute for Horticultural Plants, China Agricultural University, Beijing, 100193, China.
Xinzhong
X
Zhang
Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China; Institute for Horticultural Plants, China Agricultural University, Beijing, 100193, China.
Xuefeng
X
Xu
Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality, China; Institute for Horticultural Plants, China Agricultural University, Beijing, 100193, China. Electronic address: wangyi@cau.edu.cn.
Yi
Y
Wang
D000222:Adaptation, Physiological; D002734:Chlorophyll / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D007501:Iron / Q000378:metabolism*; D027845:Malus / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D015398:Signal Transduction
D002734:Chlorophyll; D009569:Nitric Oxide; D007501:Iron
Adaptive responses; Iron deficiency; Malus xiaojinensis; Nitric oxide