Molecular mapping of quantitative trait loci for zinc toxicity tolerance in rice seedling (Oryza sativa L.)

Excess zinc harms the growth of rice plants and zinc toxicity can easily occur in acid soils. The aim of the study was to map quantitative trait loci (QTLs) in rice for tolerance to zinc toxicity, using a recombinant inbred (RI) population derived from the cross of a japonica variety (Asominori: relatively tolerant to Zn²⁺ toxicity) with an indica variety (IR24, relatively susceptible), through 289 RFLP markers. The index scores of damage (representing Zn²⁺ toxicity tolerance), after irrigating rice seedlings with a 1000-ppm Zn²⁺ solution for 20 successive days, were examined for each RI line and its parental varieties. Continuous distributions and transgressive segregations of the index scores were observed in the RI population, suggesting that Zn²⁺ toxicity tolerance was a quantitatively inherited trait. Three QTLs for Zn²⁺ toxicity tolerance were detected on chromosomes 1, 3 and 10 and explained 21.9, 8.9 and 7.6%, respectively, of the total phenotypic variation. The results and the tightly linked molecular markers that flank the QTLs, detected in this study, will be useful in improving Zn²⁺ tolerance in rice. In addition, the genomic positions between QTLs for Zn²⁺ toxicity tolerance and the QTLs for other metal (Fe²⁺, Mn²⁺, Al³⁺) toxicity tolerances, from previous studies, are discussed.     

水稻胚芽鞘长度与抗旱性的关系及QTL定位

对由水稻品种珍汕97B和旱稻品种IRAT109构建的重组自交系195个株系的胚芽鞘长度及抗旱系数的研究表明,水分胁迫下水稻重组自交系群体的胚芽鞘长度与抗旱系数的相关系数为0.2206**。应用由213个SSR标记构建的遗传连锁图对控制胚芽鞘长度和抗旱系数的QTL进行了定位。检测到胚芽鞘长度和抗旱系数的主效QTL各为13个和5个,单个QTL对表型的贡献率为2.28%～22.65%;在第9染色体上两者的QTL出现在相同的分子标记区间（RM160-RM215）。检测到胚芽鞘长度和抗旱系数的互作位点分别为17对和3对,影响胚芽鞘长度的互作位点联合贡献率为5835%;影响抗旱系数的互作位点联合贡献率为11.93%。控制胚芽鞘长度和抗旱系数的QTL分别与其他研究中控制根系性状（深根干质量、根深、根长、根数等）的QTL位于相同的标记区间。     

Matching the Expression of Root Plasticity with Soil Moisture Availability Maximizes Production of Rice Plants Grown in an Experimental Sloping Bed having Soil Moisture Gradients

Abstract

Soil moisture distributions in rainfed lowland rice environments are largely determined by the position in the toposequence. In this study, we developed an experimental sloping bed that can simulate the soil hydrological conditions in sloping rainfed lowland rice environments to examine if the expression of promoted root system development in relation to soil moisture availability along the soil profile may maximize water uptake and dry matter production under drought. The gradient of available water along both the surface soil layer and the vertical soil profile was successfully created by manipulating ground water levels in the experimental sloping bed indicating the practical effectiveness of this experimental system. Then, two contrasting genotypes, IRAT109 (upland rice adapted japonica) and KDML105 (lowland adapted indica) were grown for plasticity evaluation. Dry matter production was maintained even at a higher position in the toposequence in IRAT109, but decreased in KDML105. Such maintenance of dry matter production in IRAT109 was attributed to its greater ability to increase root length density in a deeper soil layer, where more soil moisture is available. In contrast, KDML105 maintained root length density in the upper soil layer, and could not utilize the soil moisture available in the deeper soil layer. These results imply that the genotype that expressed root plasticity with root system developing in the soil portion where more soil moisture was available showed greater dry matter production than the genotype that showed root plasticity in the soil layer where soil moisture was less available.     

Identification of QTLs for Cadmium Tolerance During Seedling Stage and Validation of qCDSL1 in Rice

Cadmium(Cd)is a non-essential toxic metal that is harmful to plants.To investigate the genetic mechanism of Cd tolerance in rice,quantitative trait loci(QTLs)associated with Cd tolerance at the seedling stage were analyzed using a recombinant inbred line(RIL)population derived from a cross between PA64s and 93-11.A total of 36 QTLs associated with shoot length,root length,shoot dry weight,root dry weight and total dry weight were detected in Hangzhou and Lingshui of China.Among them,15 QTLs were identified under the control condition and 15 QTLs were identified under the Cd stress condition,and 6 QTLs for Cd tolerant coefficient were detected on chromosomes 1,3,7 and 9.The qCDSL1.1 and qCDSL1.2 were identified in Hangzhou and Lingshui,respectively,and had overlapping intervals on chromosome 1.To further confirm the effects of qCDSL1.1 and qCDSL1.2,we developed a chromosome segment substitution line(CSSL),CSSLqCDSL1,in 93-11 background harboring qCDSL1.1/qCDSL1.2 from PA64s.Compared to 93-11,CSSLqCDSL1 had increased shoot length under the Cd stress condition.These results pave the way for further isolation of those genes controlling Cd tolerance in rice and marker-assistant selection of rice elite varieties with Cd tolerance.     

Genetic and physiological analysis of tolerance to acute iron toxicity in rice

Background

Fe toxicity occurs in lowland rice production due to excess ferrous iron (Fe²⁺) formation in reduced soils. To contribute to the breeding for tolerance to Fe toxicity in rice, we determined quantitative trait loci (QTL) by screening two different bi-parental mapping populations under iron pulse stresses (1,000 mg L⁻¹ = 17.9 mM Fe²⁺ for 5 days) in hydroponic solution, followed by experiments with selected lines to determine whether QTLs were associated with iron exclusion (i.e. root based mechanisms), or iron inclusion (i.e. shoot-based mechanisms).

Results

In an IR29/Pokkali F₈ recombinant inbred population, 7 QTLs were detected for leaf bronzing score on chromosome 1, 2, 4, 7 and 12, respectively, individually explaining 9.2-18.7% of the phenotypic variation. Two tolerant recombinant inbred lines carrying putative QTLs were selected for further experiments. Based on Fe uptake into the shoot, the dominant tolerance mechanism of the tolerant line FL510 was determined to be exclusion with its root architecture being conducive to air transport and thus the ability to oxidize Fe²⁺ in rhizosphere. In line FL483, the iron tolerance was related mainly to shoot-based mechanisms (tolerant inclusion mechanism). In a Nipponbare/Kasalath/Nipponbare backcross inbred population, 3 QTLs were mapped on chromosomes 1, 3 and 8, respectively. These QTLs explained 11.6-18.6% of the total phenotypic variation. The effect of QTLs on chromosome 1 and 3 were confirmed by using chromosome segment substitution lines (SL), carrying Kasalath introgressions in the genetic background on Nipponbare. The Fe uptake in shoots of substitution lines suggests that the effect of the QTL on chromosome 1 was associated with shoot tolerance while the QTL on chromosome 3 was associated with iron exclusion.

Conclusion

Tolerance of certain genotypes were classified into shoot- and root- based mechanisms. Comparing our findings with previously reported QTLs for iron toxicity tolerance, we identified co-localization for some QTLs in both pluse and chronic stresses, especially on chromosome 1.     

Genetic Control of Germination Ability under Cold Stress in Rice

An F₉ recombinant inbred lines (RIL) population, derived from a cross between IR28 (Oryza sativa L. spp. indica) and Daguandao (O. sativa L. spp. japonica), was used to construct a molecular linkage map and to identify germination ability including the traits of imbibition rate, germination rate, germination index, root length, shoot length and seed vigor at 14°C for 23 d. A composite interval mapping approach was applied to conduct genetic analysis for germination ability. The frequency distributions of the germination ability traits under the cold stress in the RIL population showed continuous segregation, suggesting they were quantitative traits controlled by several genes. A total of seven QTLs were identified on chromosomes 4, 6 and 9, including two for imbibition rate (qIR-6, qIR-9), one for germination rate (qGR-4), two for germination index (qGI-4-1, qGI-4-2) and two for root length (qRL-4-1, qRL-4-2). There were no detected QTLs controlling shoot length and seed vigor. The phenotypic variance explained by a single QTL ranged from 9.1% to 37.0%, and two major QTLs, qIR-6 and qGI-4-2, accounted for over 30% of the phenotypic variance. The expressions of QTLs were developmentally regulated and growth stage-specific. Most of the QTLs observed here were located in the regions similar to the QTLs for rice cold tolerance reported previously, indicating that these QTLs were reliable. However, qRL-4-2 is not reported before.     

Differential Responses of Water Uptake Pathways and Expression of Two Aquaporin Genes to Water-Deficit in Rice Seedlings of Two Genotypes

Water-deficit(WD) is a major abiotic stress constraining crop productivity worldwide. Zhenshan 97 is a drought-susceptible rice genotype, while IRAT109 is a drought-resistant one. However, the physiological basis of the difference remains unclear. These two genotypes had similar total water uptake rates under both WD and well-watered(WW) conditions, and their water uptake rates under WD were significantly decreased compared with those under WW. However, the water uptake rate via the cell-to-cell pathway was significantly increased in Zhenshan 97 but decreased in IRAT109 under WD, whereas the opposite trends were observed through the apoplastic pathway. These results indicated that the stress responses and relative contributions of these two water uptake pathways were associated with rice genotype under WD. The expression levels of OsPIP2;4 and OsPIP2;5 genes were significantly higher in roots of Zhenshan 97 than in IRAT109 under the two conditions. OsPIP2;4 expression in roots was significantly up-regulated under WD, while OsPIP2;5 expression showed no significant change. These results suggest that the expression levels of OsPIP2;4 and OsPIP2;5 in rice are dependent on genotype and water availability. Compared with Zhenshan 97, IRAT109 had a higher root dry weight, water uptake rate and xylem sap flow rate, and lower leaf water potential and root porosity under WD, which might be responsible for the drought resistance in IRAT109.     

QTL analysis of panicle morphology response to irrigation regime in aerobic rice culture

In water-efficient rice production, grain yield is often constrained by panicle size. The objective of this study was to genetically dissect the response of panicle morphology to irrigation regimes in aerobic rice culture. We grew ‘Akihikari’ (a lowland japonica cultivar) × ‘IRAT109’ (an upland japonica cultivar) backcross inbred lines in aerobic soils with full or limited irrigation for 2 years, and examined 4 panicle traits—number of florets per panicle (FPP), number of primary branches per panicle (BPP), number of florets per primary branch (FPB), and frequency of pre-flowering floret abortion (%FA)—and grain yield. QTLs for BPP were detected in both the irrigation regimes but QTLs for FPB and %FA were detected mostly only in either of the irrigation regimes. The QTL for FPP on chromosome 2 (RM3421–RM213) coincided with that for yield under full irrigation, showing that this QTL is related to sink capacity and yield potential in aerobic rice culture. On the other hand, the QTL for FPB on chromosome 1 (RM3148–RM243) coincided with that for yield under limited irrigation, when water deficit was moderate. The QTL for root axis length at vegetative stage, previously identified in the same mapping population, was located near this region. This study unravelled the complicated genetic control on panicle morphology in aerobic rice culture, and suggested the positive roles of the dehydration avoidance mechanism by vigorous root growth on panicle size and yield under dry soil conditions.     

Inheritance and QTL Mapping of Salt Tolerance in Rice

An F2 population derived from the cross between Jiucaiqing (japonica) and IR36 (indica) was used to analyze the inheritance of salt tolerance in rice by genetic model of major-genes plus polygenes, and to map the corresponding QTLs by SSR molecular markers. Rice plants of P1, P2, F1 and F2 at 5- to 6- leaf stage were treated under 140 mmol/L NaCI for 10 days. Three indices representing the ability of salt tolerance of rice seedlings were measured, including salt tolerance rating (STR), Na^ /K^ ratio in roots and dry matter weight of shoots (DWS). STR, Na^ /K^ and DWS were all controlled by two major genes with modification by polygenes. Heritability of these traits from major genes was 17.8, 53.3 and 52.3%, respectively. The linkage map constructed by 62 SSR molecular markers covered a total length of about 1 142 cM. There were three QTLs detected for STR located on chromosome 1, 5 and 9, two QTLs for DWS on chromosomes 8 and 9, and two QTLs for Na^ /K^ on chromosomes 2 and 6, one on each chromosome respectively. Single QTL accounted for 6.7 to 19.3% of phenotypic variation. Identification method of salt tolerance in rice and breeding of rice varieties with salt tolerance based on molecular markers assisted selection had been discussed.     

6-BA对Hg2+胁迫下小麦幼苗渗透调节物质及抗氧化特性的影响

为探讨6-苄氨基腺嘌呤(6-BA)对Hg2+胁迫下小麦幼苗生长的调节作用,采用营养液水培法,以小麦品种807为材料,分析了叶面喷施不同浓度的6-BA对Hg2+胁迫下小麦幼苗叶片中渗透调节物质含量、抗氧化酶活性及抗氧化物质含量的影响。结果表明,50mg·L-1 HgCl2处理后,小麦幼苗叶片的可溶性糖和可溶性蛋白含量显著降低,过氧化物酶(POD)和超氧化物歧化酶(SOD)活性下降,还原型抗坏血酸(AsA)和还原型谷胱甘肽(GSH)含量显著降低。叶面喷施一定浓度的6-BA能够提高Hg2+胁迫下小麦幼苗叶片的可溶性糖和可溶性蛋白含量,显著提高小麦幼苗叶片的POD、SOD活性和AsA、GSH含量,降低脱氢抗坏血酸(DHA)和氧化型谷胱甘肽(GSSG)含量,提高小麦幼苗叶片的AsA/DHA和GSH/GSSG比值,从而缓解Hg2+胁迫对小麦幼苗生长的抑制作用。叶面喷施10mg·L-1 6-BA对缓解小麦幼苗Hg2+胁迫效果最好。     

Root plasticity under fluctuating soil moisture stress exhibited by backcross inbred line of a rice variety,Nipponbare carrying introgressed segments from KDML105 and detection of the associated QTLs

In rainfed lowland rice ecosystem, rice plants are often exposed to alternating recurrences of waterlogging and drought due to erratic rainfall. Such soil moisture fluctuation (SMF) which is completely different from simple or progressive drought could be stressful for plant growth, thereby causing reduction in yield. Root plasticity is one of the key traits that play important roles for plant adaptation under such conditions. This study aimed to evaluate root plasticity expression and its functional roles in dry matter production and yield under SMF using Nipponbare, KDML 105 and three backcross inbred lines (BILs) and to identify QTL(s) associated with root traits in response to SMF at two growth stages using Nipponbare/KDML105 F₂ plants. A BIL, G3-3 showed higher shoot dry matter production and yield than Nipponbare due to its greater ability to maintain stomatal conductance concomitant with greater root system development caused by promoted production of nodal and lateral roots under SMF. QTLs were identified for total nodal root length, total lateral root length, total root length, number of nodal roots, and branching index under SMF at vegetative and reproductive stages. The QTLs detected at vegetative and reproductive stages were different. We discuss here that relationship between root system of G3-3 and the detected QTLs. Therefore, G3-3 and the identified QTLs could be useful genetic materials in breeding program for improving the adaptation of rice plants in target rainfed lowland areas.     

外源水杨酸对Hg~(2+)胁迫下小麦幼苗生长及生理的影响

为了解水杨酸(SA)对Hg2+胁迫小麦幼苗生长的缓解作用,以小麦品种豫麦58号为材料,采用室内水培法分析了在Hg2+胁迫下小麦幼苗经不同浓度SA处理后的生长及生理变化。结果表明,外施SA能显著提高Hg2+胁迫下小麦幼苗的根长、株高、单株鲜重,叶片叶绿素、脯氨酸和可溶性蛋白含量,以及抗氧化酶活性和根系活力(P0.05),极显著降低丙二醛含量与超氧阴离子产生速率(P0.01)。说明外施SA可通过提高小麦幼苗可溶性蛋白和脯氨酸含量及抗氧化酶活性来维持细胞膜的稳定性,降低膜脂过氧化伤害程度,从而缓解了Hg2+胁迫对幼苗生长的抑制作用,其中以40mg·L-1 SA缓解效果最好。     

Calcium Signaling is Involved in Negative Phototropism ofRice Seminal Roots简

Calcium ions(Ca2+) act as an intracellular second messenger and affect nearly all aspects of cellular life. They are functioned by interacting with polar auxin transport, and the negative phototropism of plant roots is caused by the transport of auxin from the irradiated side to the shaded side of the roots. To clarify the role of calcium signaling in the modulation of rice root negative phototropism, as well as the relationship between polar auxin transport and calcium signaling, calcium signaling reagents were used to treat rice seminal roots which were cultivated in hydroculture and unilaterally illuminated at an intensity of 100–200 μmol/(m2·s) for 24 h. Negative phototropism curvature and growth rate of rice roots were both promoted by exogenous CaCl2 lower than 100 μmol/L, but inhibited by calcium channel blockers(verapamil and LaCl3), calcineurin inhibitor(chlorpromazine, CPZ), and polar auxin transport inhibitor(N-1-naphthylphthalamic acid, NPA). Roots stopped growing and negative phototropism disappeared when the concentrations increased to 100 μmol/L verapamil, 12.500 μmol/L LaCl3, 60 μmol/L CPZ, and 6 μmol/L NPA. Moreover, 100 μmol/L CaCl2 could relieve the inhibition of LaCl3, verapamil and NPA. The enhanced negative phototropism curvature was caused by the transportation of more auxin from the irradiated side to the shaded side in the presence of exogenous Ca2+. Calcium signaling plays a key role as a second messenger in the process of light signal regulation of rice root growth and negative phototropism.     

Mapping of QTLs for Germination Characteristics under Non-stress and Drought Stress in Rice

Identification of genetic factors controlling traits associated with seed germination under drought stress conditions, leads to identification and development of drought tolerant varieties. Present study by using a population of F2：, derived from a cross between a drought tolerant variety, Gharib （indica） and a drought sensitive variety, Sepidroud （indica）, is to identify and compare QTLs associated with germination traits under drought stress and non-stress conditions. Through QTL analysis, using composite interval mapping, regarding traits such as germination rate （GR）, germination percentage （GP）, radicle length （RL）, plumule length （PL）, coleorhiza length （COL） and coleoptile length （CL）, totally 13 QTLs were detected under pole drought stress （-8 MPa poly ethylene glycol 6000） and 9 QTLs under non-stress conditions. Of the QTLs identified under non-stress conditions, QTLs associated with COL （qCOL-5） and GR （qGR-1） explained 21.28% and 19.73% of the total phenotypic variations, respectively Under drought stress conditions, QTLs associated with COL （qCOL-3） and PL （qPL-5） explained 18.34% and 18.22% of the total phenotypic variations, respectively. A few drought-tolerance-related QTLs identified in previous studies are near the QTLs detected in this study, and several QTLs in this study are novel alleles. The major QTLs like qGR-1, qGP-4, qRL-12 and qCL-4 identified in both conditions for traits GR, GP, RL and CL, respectively, should be considered as the important and stable trait-controlling QTLs in rice seed germination. Those major or minor QTLs could be used to significantly improve drought tolerance by marker-assisted selection in rice.     

玉米自交系耐盐种质的筛选及耐盐性评价

在0+0、2.5+2.5、5+5和7.5+7.5 mmol/L（Na₂CO₃+NaHCO₃）盐浓度胁迫下,对118份玉米自交系芽期、苗期的耐盐性差异进行比较,以主要农艺性状综合表现为依据筛选耐盐种质。各指标受盐害影响程度大小顺序为株高>芽势>叶长>根长>地上含水量>地下含水量>叶宽>芽率>须根数>根冠比>茎粗>根粗;当盐胁迫溶液为7.5 mmol/LNa₂CO₃+7.5 mmol/L NaHCO₃时,对玉米自交系影响差异显著。综合各个指标的盐害率对118份玉米自交系进行评价和排序,5个耐盐性强的自交系品种为DL、A71、PHB1M、A92和WM33;对盐敏感的5个品种为06NY-25、Mo17、郑32、南引26和农M1。     

6-BA浸种对HgCl2胁迫下小麦种子萌发和幼苗生长的影响

为探讨6-苄基腺嘌呤（6-BA）浸种对HgCl₂胁迫下小麦种子萌发及其幼苗生长的缓解作用,以3个小麦品种为材料,研究了不同浓度6-BA浸种对200 mg·L^-1HgCl₂胁迫下小麦种子发芽、幼苗生长、抗氧化酶活性、可溶性蛋白和丙二醛含量的影响。结果表明,200 mg·L^-1HgCl₂处理后,3个小麦品种种子的发芽势、发芽率、根长、芽长和鲜重降低,幼苗的抗氧化酶活性和可溶性蛋白含量降低,丙二醛含量增加。一定浓度6-BA浸种可以缓解HgCl₂胁迫对小麦种子萌发的抑制作用,但对小麦的根长、芽长和鲜重的影响因小麦品种而不同。HgCl₂胁迫下,3个小麦品种幼苗的SOD、POD活性和可溶性蛋白含量随着6-BA浓度的增加均基本呈先升高后降低的趋势,最佳6-BA浓度因品种而不同;3个小麦品种的MDA含量均呈先降低后升高的趋势,以6-BA浓度为15 mg·L^-1时MDA含量最低。说明一定浓度6-BA浸种能够缓解HgCl₂胁迫对小麦种子萌发和幼苗生长的毒害作用,但最佳6-BA浓度因小麦品种的不同而不同。     

Relationship Between Coleoptile Length and Drought Resistance and Their QTL Mapping in Rice

By using a set of recombinant inbred line(RIL)population involving in 195 lines derived from a cross of Zhenshan 97B (lowland variety)and IRAT109(upland variety),the correlation analysis between coleoptile length(CL)and drought resistance index (DRI)and their QTL identification were conducted.There existed a significantly positive relationship between CL and DRI with the correlation coefficient of 0.2206**under water stress conditions.Under normal and water stress conditions,a total of eleven and four QTLs for CL and DRI,respectively,were detected on chromosomes 1,2,4,5,6,7,9,11 and 12 by using a linkage map including 213 SSR markers,which explained 4.84%to 22.65%of phenotypic variance.Chromosomes 1 and 9 possessing the QTLs for DRI harbored simultaneously QTLs for CL,and qCL9 shared the same chromosome location with qDRI9(RM160-RM215).Comparing the QTLs related to drought resistance in other studies,QTLs for CL and DRI were located in the same or adjacent marker interval as those related to root traits,such as number,dry weight,depth,and length of root.Moreover,sixteen and three pairs of epistatic loci for CL and DRI were found,which accounted for 56.17%and 11.93%of the total variation in CL and DRI,respectively.     

Saline-Alkali Tolerance in Rice: Physiological Response,Molecular Mechanism,and QTL Identification and Application to Breeding

Salinity-alkalinity is incipient abiotic stress that impairs plant growth and development. Rice (Oryza sativa) is a major food crop greatly affected by soil salinity and alkalinity, requiring tolerant varieties in the saline-alkali prone areas. Understanding the molecular and physiological mechanisms of saline-alkali tolerance paves the base for improving saline-alkali tolerance in rice and leads to progress in breeding. This review illustrated the physiological consequences, and molecular mechanisms especially signaling and function of regulating genes for saline-alkali tolerance in rice plants. We also discussed QTLs regarding saline-alkali tolerance accordingly and ways of deployment for improvement. More efforts are needed to identify and utilize the identified QTLs for saline-alkali tolerance in rice.     

Comparison of Root System Development in Two Rice Cultivars During Stress Recovery from Drought and the Plant Traits for Drought Resistance

Summary

A greenhouse experiment was conducted to compare root system development of two upland rice cultivars, IRAT 13 and Senshou, during recovery from drought stress and to identify the plant traits that confer drought resistance. From 62 days after sowing (62 DAS), drought stress was given for 6 d followed by rewatering for 14 d. Root length density (RLD) and root diameter (thickness) were measured at the end of the stress and rewatering periods. Control plants were well-watered throughout the study. Gultivar IRAT 13 had thicker roots and higher relative RLD (ratio of RLD in drought-stressed plants to that in control plants) than under drought stress, and significantly higher root growth recovery after rewatering cultivar Senshou. Related plant traits such as evapotranspiration (ET), leaf and stem dry weights and weight of senescent leaves (dead leaves) in IRAT 13 were significantly more favorable for drought resistance compared to Senshou.     

Physiological and Proteomic Analyses Reveal Effects of Putrescine-Alleviated Aluminum Toxicity in Rice Roots

The effects of putrescine on improving rice growth under aluminum(Al) toxicity conditions have been previously demonstrated, however, the underlying mechanism remains unclear. In this study, treatment with 50 μmol/L Al significantly decreased rice root growth and whole rice dry weight, inhibited Ca~(2+) uptake, decreased ATP synthesis, and increased Al, H_2O_2 and malondialdehyde(MDA) contents, whereas the application of putrescine mitigated these negative effects. Putrescine increased root growth and total dry weight of rice, reduced total Al content, decreased H_2O_2 and MDA contents by increasing antioxidant enzyme(superoxide dismutase, peroxidase, catalase and glutathione S-transferase) activities, increased Ca~(2+) uptake and energy production. Proteomic analyses using data-independent acquisition successfully identified 7 934 proteins, and 59 representative proteins exhibiting fold-change values higher than 1.5 were randomly selected. From the results of the proteomic and biochemical analyses, we found that putrescine significantly inhibited ethylene biosynthesis and phosphorus uptake in rice roots, increased pectin methylation, decreased pectin content and apoplastic Al deposition in rice roots. Putrescine also alleviated Al toxicity by repairing damaged DNA and increasing the proteins involved in maintaining plasma membrane integrity and normal cell proliferation. These findings improve our understanding of how putrescine affects the rice response to Al toxicity, which will facilitate further studies on environmental protection, crop safety, innovations in rice performance and real-world production.