Reduced ABA Accumulation in the Root System is Caused by ABA Exudation in Upland Rice (Oryza sativa L. var. Gaoshan1) and this Enhanced Drought Adaptation.
Lowland rice (Nipponbare) and upland rice (Gaoshan 1) that are comparable under normal and moderate drought conditions showed dramatic differences in severe drought conditions, both naturally occurring long-term drought and simulated rapid water deficits. We focused on their root response and found that enhanced tolerance of upland rice to severe drought conditions was mainly due to the lower level of ABA in its roots than in those of the lowland rice. We first excluded the effect of ABA biosynthesis and catabolism on root-accumulated ABA levels in both types of rice by monitoring the expression of four OsNCED genes and two OsABA8ox genes. Next, we excluded the impact of the aerial parts on roots by suppressing leaf-biosynthesized ABA with fluridone and NDGA (nordihydroguaiaretic acid), and measuring the ABA level in detached roots. Instead, we proved that upland rice had the ability to export considerably more root-sourced ABA than lowland rice under severe drought, which improved ABA-dependent drought adaptation. The investigation of apoplastic pH in root cells and root anatomy showed that ABA leakage in the root system of upland rice was related to high apoplastic pH and the absence of Casparian bands in the sclerenchyma layer. Finally, taking some genes as examples, we predicted that different ABA levels in rice roots stimulated distinct ABA perception and signaling cascades, which influenced its response to water stress.
CAS Key Laboratory for Biomedical Effects of Nanomaterials & Nanosafety, National Center for Nanoscience and Technology of China, Beijing 100190, China Department of Biology, Hong Kong Baptist University, Hong Kong, China.
Lu
L
Shi
State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, China.
Miaomiao
M
Guo
Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China.
Nenghui
N
Ye
State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, China.
Yinggao
Y
Liu
Department of Biology, Hong Kong Baptist University, Hong Kong, China.
Rui
R
Liu
Department of Biology, Hong Kong Baptist University, Hong Kong, China.
Yiji
Y
Xia
College of Life Sciences, Capital Normal University, Beijing, China.
Suxia
S
Cui
Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong, China jhzhang@cuhk.edu.hk.
Jianhua
J
Zhang
D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D000222:Adaptation, Physiological / Q000187:drug effects; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003681:Dehydration; D055864:Droughts; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D006863:Hydrogen-Ion Concentration; D012275:Oryza / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D010940:Plant Proteins; D018517:Plant Roots / Q000033:anatomy & histology / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000494:pharmacology; D011392:Proline / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013997:Time Factors
D010940:Plant Proteins; D012333:RNA, Messenger; D011092:Polyethylene Glycols; D000040:Abscisic Acid; D003577:Cytochrome P-450 Enzyme System; D011392:Proline; C107203:abscisic acid 8'-hydroxylase
ABA accumulation; Lowland and upland rice; Root system; Sclerenchyma layer; Water stress; pH