The auxin transporter OsAUX1 regulates tillering in rice(Oryza sativa)

Tillering is an important agronomic trait of rice(Oryza sativa)that affects the number of effective panicles,thereby affecting yields.The phytohormone auxin plays a key role in tillering.Here we identified the high tillering and semi-dwarf 1(htsd1)mutant with auxin-deficiency root characteristics,such as shortened lateral roots,reduced lateral root density,and enlarged root angles.htsd1 showed reduced sensitivity to auxin,but the external application of indole-3-acetic acid(IAA)inhibited its tillering.We identified the mutated gene in htsd1 as AUXIN1(OsAUX1,LOC_Os01g63770),which encodes an auxin influx transporter.The promoter sequence of OsAUX1 contains many SQUAMOSA PROMOTER BINDING PROTEIN-LIKE(SPL)binding sites,and we demonstrated that SPL7 binds to the OsAUX1 promoter.TEOSINTE BRANCHED1(OsTB1),a key gene that negatively regulates tillering,was significantly downregulated in htsd1.Tillering was enhanced in the OsTB1 knockout mutant,and the external application of IAA inhibited tiller elongation in this mutant.Overexpressing OsTB1 restored the multi-tiller phenotype of htsd1.These results suggest that SPL7 directly binds to the OsAUX1 promoter and regulates tillering in rice by altering OsTB1 expression to modulate auxin signaling.

Irrigation regimes modulate non-structural carbohydrate remobilization and improve grain filling in rice(Oryza sativa L.)by regulating starch metabolism

Recently developed ‘super’ rice cultivars with greater yield potentials often suffer from the problem of poor grain filling, especially in inferior spikelets. Here, we studied the activities of enzymes related to starch metabolism in rice stems and grains, and the microstructures related to carbohydrate accumulation and transportation to investigate the effects of different water regimes on grain filling. Two ‘super’ rice cultivars were grown under two irrigation regimes of well-watered(WW) and alternate wetting and moderate soil drying(AWMD). Compared with the WW treatment,the activities of ADP glucose pyrophosphorylase(AGPase), starch synthase(StSase) and starch branching enzyme(SBE), and the accumulation of non-structural carbohydrates(NSCs) in the stems before heading were significantly improved, and more starch granules were stored in the stems in the AWMD treatment. After heading, the activities of α-amylase, β-amylase, sucrose phosphate synthase(SPS) and sucrose synthase in the synthetic direction(SSs)were increased in the stems to promote the remobilization of NSCs for grain filling under AWMD. During grain filling, the enzymatic activities of sucrose synthase in the cleavage direction(SSc), AGPase, StSase and SBE in the inferior spikelets were increased, which promoted grain filling, especially for the inferior spikelets under AWMD.However, there were no significant differences in vascular microstructures. The grain yield and grain weight could be improved by 13.1 and 7.5%, respectively, by optimizing of the irrigation regime. We concluded that the low activities of key enzymes in carbon metabolism is the key limitation for the poor grain filling, as opposed to the vascular microstructures, and AWMD can increase the amount of NSC accumulation in the stems before heading, improve the utilization rate of NSCs after heading, and increase the grain filling, especially in the inferior spikelets, by altering the activities of key enzymes in carbon metabolism.

Conventional Breeding and Molecular Markers for Blast Disease Resistance in Rice (Oryza sativa L.)

Monogenic lines,which carried 23 genes for blast resistance were tested and used donors to transfer resistance genes by crossing method.The results under blast nursery revealed that 9 genes from 23 genes were susceptible to highly susceptible under the three locations(Sakha,Gemmeza,and Zarzoura in Egypt);Pia,Pik,Pik-p,Piz-t,Pita,Pi b,Pi,Pi 19 and Pi 20.While,the genes Pii,Pik-s,Pik-h,Pi z,Piz-5,Pi sh,Pi 3,Pi 1,Pi 5,Pi 7,Pi 9,Pi 12,Pikm and Pita-2 were highly resistant at the same locations.Clustering analysis confirmed the results,which divided into two groups;the first one included all the susceptible genes,while the second one included the resistance genes.In the greenhouse test,the reaction pattern of five races produced 100%resistance under artificial inoculation with eight genes showing complete resistance to all isolates.The completely resistant genes:Pii,Pik-s,Piz,Piz-5(=bi2)(t),Pita(=Pi4)(t),Pita,Pi b and Pi1 as well as clustering analysis confirmed the results.In the F1 crosses,the results showed all the 25 crosses were resistant for leaf blast disease under field conditions.While,the results in F2 population showed seven crosses with segregation ratio of 15(R):1(S),two cross gave segregated ratio of 3 R:1 S and one gave 13:3.For the identification of blast resistance genes in the parental lines,the marker K3959,linked to Pik-s gene and the variety IRBLKS-F5 carry this gene,which was from the monogenic line.The results showed that four genotypes;Sakha 105,Sakha 103,Sakha 106 and IRBLKS-F5 were carrying Pik-s gene,while was absent in the Sakha 101,Sakha 104,IRBL5-M,IRBL9-W,IRBLTACP1 and IRBL9-W(R)genotypes.As for Pi 5 gene,the results showed that it was present in Sakha 103 and Sakha 104 varieties and absent in the rest of the genotypes.In addition,Pita-Pita-2 gene was found in the three Egyptian genotypes(Sakha 105,Sakha 101 and Sakha 104)plus IRBLTACP1 monogenetic.In F2 generation,six populations were used to study the inheritance of blast resistance and specific primers to confirm the ratio and identify the resistance genes.However,the ratios in molecular markers were the same of the ratio under field evaluation in the most population studies.These findings would facilitate in breeding programs for gene pyramiding and gene accumulation to produce durable resistance for blast using those genotypes.

基于水稻大粒染色体片段代换系Z29的鉴定及QTL定位

千粒质量作为水稻产量的三要素之一,对产量的影响较大,其中千粒质量主要受水稻粒型的影响,因此挖掘新的粒型基因在生产中具有重要的意义.研究选育到1个以日本晴为受体亲本、自育优良籼稻恢复系R225为供体亲本的水稻染色体片段代换系(CSSL)Z29. Z29含有来自R225的10个代换片段,平均代换长度2.90 Mb. Z29粒长和粒宽均极显著增加,表现为大粒表型,且其籽粒变大是由颖壳细胞数量极显著增多、增大引起.利用日本晴与Z29杂交构建的次级F2群体进行QTL定位,共检测到8个粒型相关QTL.进一步利用MAS法在F3群体中选育出14个次级染色体片段代换系,包括4个单片段代换系、 5个双片段代换系、 2个三片段代换系和3个四片段代换系.结果可为目的粒型相关QTL克隆和分子机制解析奠定基础,为分子设计育种提供资源.

Comparative study of QTLs for agronomic traits of rice (Oriza sativa L.) between salt stress and nonstress environment

Genotype-by-environment interactions (GxE) are commonly observed for quantitative traits. In the present study, a doubled haploid (DH) population and its genetic linkage map were used to comparatively study QTLs in salt stress and nonstress environments. A total of 24 QTLs were detected for five agronomic traits, which were distributed on all the chromosomes except 9 and 11. Under the salt stress, nine (37.5%) QTLs were detected, including one for 1 000-grain weight (GW), two for heading date (HD), one for plant height (PH), two for grains per panicle (GPP), and three for effective tillers (ET), while in the nonstress environment, 17 QTLs (70.8%) were detected, including five for GW, six for HD, three for PH, two for GPP, and one for ET. Two QTLs (8.3%) were consistently detected in both environments. One was identified on chromosome 4 for HD and the other on Chr.6 for GPP. Furthermore, three regions carrying multiple QTLs were identified on chromosomes 1, 4 and 8 respectively. For example, on chromosome 8, three QTLs for HD, GW and PH, respectively were identified between RG885-GA408 in nonstress environment, but not in the stress environment. The comparative study of QTLs detected in extremely different (salt stress and nonstress) environments revealed that there existed several QTLs for important agronomic traits on chromosome 8 which were affected significantly by salt stress.

DROUGHT-INDUCED UNKNOWN PROTEIN 1 positively modulates drought tolerance in cultivated alfalfa(Medicago sativa L.)

Alfalfa is the most widely cultivated perennial legume forage crop worldwide.Drought is one of the major environmental factors influencing alfalfa productivity.However,the molecular mechanisms underlying alfalfa responses to drought stress are still largely unknown.This study identified a drought-inducible gene of unknown function,designated as Medicago sativa DROUGHT-INDUCED UNKNOWN PROTEIN 1(MsDIUP1).MsDIUP1 was localized to the nucleus,chloroplast,and plasma membranes.Overexpression of MsDIUP1 in Arabidopsis resulted in increased tolerance to drought,with higher seed germination,root length,fresh weight,and survival rate than in wild-type(WT)plants.Consistently,analysis of MsDIUP1 over-expression(OE)alfalfa plants revealed that MsDIUP1 also increased tolerance to drought stress,accompanied by physiological changes including reduced malondialdehyde(MDA)content and increased osmoprotectants accumulation(free proline and soluble sugar),relative to the WT.In contrast,disruption of MsDIUP1 expression by RNA interference(RNAi)in alfalfa resulted in a droughthypersensitive phenotype,with a lower chlorophyll content,higher MDA content,and less osmoprotectants accumulation than that of the WT.Transcript profiling of alfalfa WT,OE,and RNAi plants during drought stress showed differential responses for genes involved in stress signaling,antioxidant defense,and osmotic adjustment.Taken together,these results reveal a positive role for MsDIUP1 in regulating drought tolerance.

全基因组关联分析定位水稻分蘖角度QTL

【目的】水稻分蘖角度是影响水稻产量的关键农艺性状,挖掘水稻分蘖角度QTL(基因)及其优势单倍型,有助于构建水稻理想株型。【方法】以333份来自水稻3K资源的核心种质为研究材料,于2020年和2022年分别在湖南农业大学耘园基地和春华基地种植,在抽穗期测量分蘖角度,结合基因型,利用TASSEL 5.2的MLM模型进行全基因组关联分析。【结果】共检测到6个分蘖角度QTL位点,分布在水稻2、5、6、9和12号染色体上,分别命名为qTA2、qTA5、qTA6.1、qTA6.2、qTA9和qTA12,这些QTL的表型贡献率为6.23%~16.22%。除了qTA9与分蘖角度主效QTL TAC1共定位外,其余5个QTL均为新的位点。进一步对5个QTL位点进行候选基因分析,初步筛选到qTA2和qTA6.1的候选基因别为Os02g0817900和Os06g0682800,候选基因Os02g0817900编码水稻细胞色素P450家族蛋白,候选基因Os06g0682800编码锌指结构域蛋白。【结论】本研究挖掘到新的水稻分蘖角度相关位点并对候选基因进行了分析,为分蘖角度新QTL(基因)的克隆以及分蘖角度的遗传改良提供参考。

一个新的水稻黄绿叶突变体ygl-9108的鉴定与基因定位

本研究旨在对水稻黄绿叶突变体ygl-9108进行表型分析和基因定位,为后续图位克隆该叶色相关基因奠定基础。以黄绿叶突变体ygl-9108为试材,利用突变体ygl-9108和‘五山丝苗’杂交的F2群体进行基因定位。结果表明,与野生型相比,突变体的株高、有效穗数、穗长、每穗粒数、结实率、粒宽、千粒重和单株谷重均显著下降,下降比例分别为21.5%、21.2%、14.6%、19.2%、11.0%、10.2%、12.9%和52.2%。透射电镜观察显示,突变体叶肉细胞的叶绿体数量大量减少,类囊体结构异常。遗传分析表明,突变体的表型由一个隐性核基因控制。利用图位克隆方法,ygl-9108被定位于水稻第11号染色体两InDel标记11Y39和11Y45之间,物理距离约为147 kb,该区间内未见有叶色相关基因的报道,表明ygl-9108是一个新的黄绿叶调控基因。本研究结果为ygl-9108的克隆和功能分析奠定了坚实的基础。

The OsBSK1-2-MAPK module regulates blast resistance in rice

Receptor-like cytoplasmic kinase OsBSK1-2 was reported to play an important role in regulation of response to rice blast,but the signaling pathway remained unknown.In this study,we identified OsMAPKKK18 and previously uncharacterized MAPKKKs OsMAPKKK16 and OsMAPKKK19 that interact with OsBSK1-2.Expression of all three MAPKKKs was induced by Magnaporthe oryzae infection,and all three induced cell death when transiently expressed in Nicotiana benthamiana leaves.Knockout of OsMAPKKK16 and OsMAPKKK18 compromised blast resistance and overexpression of OsMAPKKK19 increased blast resistance,indicating that all three MAPKKKs are involved in regulation of rice blast response.Furthermore,both OsMAPKKK16 and OsMAPKKK19 interacted with and phosphorylated OsMKK4 and OsMKK5,and chitin-induced MAPK activation was suppressed in osmapkkk16 and osbsk1-2 mutants.OsMAPKKK18 was earlier reported to interact with and phosphorylate OsMKK4 and affect chitin-induced MAPK activation,suggesting that OsBSK1-2 is involved in regulation of immunity through multiple MAPK signaling pathways.Unlike BSK1 in Arabidopsis,OsBSK1-2 was not involved in response to avirulent M.oryzae strains.Taken together,our results revealed important roles of OsMAPKKK16/18/19 and a OsBSK1-2-OsMAPKKK16/18/19-OsMKK4/5 module in regulating response to rice blast.

OsWRKY65 enhances immunity against fungal and bacterial pathogens in rice

Diverse bacterial and fungal pathogens attack plants,causing biotic stress and severe yield losses globally.These losses are expected to become more serious as climate change improves conditions for many pathogens.Therefore,identifying genes conferring broad-spectrum disease resistance and elucidating their underlying mechanisms provides important resources for plant breeding.WRKY transcription factors affect plant growth and stress responses.However,the functions of many WRKY proteins remain to be elucidated.Here,we demonstrated the role of rice(Oryza sativa)WRKY groupⅢtranscription factor OsWRKY65 in immunity.OsWRKY65 localized to the nucleus and acted as transcriptional repressor.Genetic and molecular functional analyses showed that OsWRKY65 increases resistance to the fungal pathogen Fusarium fujikuroi through downregulation of GA signaling and upregulation of JA signaling.Moreover,OsWRKY65 modulated the expression of the key genes that confer susceptibility or resistance to Xanthomonas oryzae pv.oryzae to enhance immunity against the pathogen.In particular,OsWRKY65directly bound to the promoter region of OsSWEET13 and repressed its expression.Taken together,our findings demonstrate that the OsWRKY65 enhances resistance to fungal and bacterial pathogens in rice.

A Farmer’s Approach to Detecting Photoperiod Sensitivity in Rice (Oryza sativa ssp. indica) Landraces

Most indigenous rice landraces are sensitive to photoperiod during short day seasons,and this sensitivity is more pronounced in indica than in japonica landraces.Attempts to identify photoperiod sensitive(PPS)cultivars based on the life history stages of the rice plant,and several models and indices based on phenology and day length have not been precise,and in some cases yield counterfactual inferences.Following the empirical method of traditional Asian rice farmers,the author has developed a robust index,based on the sowing and flowering dates of a large number of landraces grown in different seasons from 2020 to 2023,to contradistinguish PPS from photoperiod insensitive cultivars.Unlike other indices and models of photoperiod sensitivity,the index does not require the presumed duration of different life history stages of the rice plant but relies only on the flowering dates and the number of days till flowering of a rice cultivar sown on different dates to consistently identify photoperiod sensitive cultivars.

The response of roots and the rhizosphere environment to integrative cultivation practices in paddy rice

Integrative cultivation practices(ICPs)are essential for enhancing cereal yield and resource use efficiency.However,the effects of ICP on the rhizosphere environment and roots of paddy rice are still poorly understood.In this study,four rice varieties were produced in the field.Each variety was treated with six different cultivation techniques,including zero nitrogen application(0 N),local farmers’practice(LFP),nitrogen reduction(NR),and three progressive ICP techniques comprised of enhanced fertilizer N practice and increased plant density(ICP1),a treatment similar to ICP1 but with alternate wetting and moderate drying instead of continuous flooding(ICP2),and the same practices as ICP2 with the application of organic fertilizer(ICP3).The ICPs had greater grain production and nitrogen use efficiency than the other three methods.Root length,dry weight,root diameter,activity of root oxidation,root bleeding rate,zeatin and zeatin riboside compositions,and total organic acids in root exudates were elevated with the introduction of the successive cultivation practices.ICPs enhanced nitrate nitrogen,the activities of urease and invertase,and the diversity of microbes(bacteria)in rhizosphere and non-rhizosphere soil,while reducing the ammonium nitrogen content.The nutrient contents(ammonium nitrogen,total nitrogen,total potassium,total phosphorus,nitrate,and available phosphorus)and urease activity in rhizosphere soil were reduced in all treatments in comparison with the non-rhizosphere soil,but the invertase activity and bacterial diversity were greater.The main root morphology and physiology,and the ammonium nitrogen contents in rhizosphere soil at the primary stages were closely correlated with grain yield and internal nitrogen use efficiency.These findings suggest that the coordinated enhancement of the root system and the environment of the rhizosphere under integrative cultivation approaches may lead to higher rice production.

水稻早衰突变体psl4(t)的表型鉴定及基因定位

水稻叶片早衰严重影响水稻的产量与品质,挖掘水稻叶片早衰相关基因并解析其分子机制,对提高水稻产量具有重要意义.从涪恢9802和LR杂交后代中筛选到叶早衰突变体psl4(t),该突变体6叶期前叶片呈正常绿色,从7叶期至剑叶(倒1叶)期每张叶片均是从叶尖至叶中部逐渐衰老,叶片的叶绿体发育受阻其体积变小、光合色素质量分数减少,叶片提前衰老.农艺性状分析结果表明:与野生型相比,突变体psl4(t)的穗长、有效分蘖数和籽粒宽变化无统计学意义,而株高、每穗粒数、结实率及千粒质量显著降低.遗传分析结果发现:突变体psl4(t)的早衰性状受单隐性核基因控制,利用分子标记将目标基因定位于第4染色体长臂端两个SSR标记(RM17004和RM17006)之间38.5 kb的范围内.研究为psl4(t)基因的克隆及功能解析、早衰分子机制研究奠定基础.

亚热带地区水稻(Oryza sativa L.)气孔臭氧通量和产量的响应关系

基于开放式臭氧浓度升高O_3-FACE(Free-Air Concentration Elevation of O_3)实验平台,利用前期水稻O_3-FACE试验的基础数据,通过建立水稻产量与不同评价指标(累积气孔O_3吸收通量PODY和O_3浓度指标AOTX)的响应关系,比较了水稻产量损失与各评价指标的相关性差异,通过对暴露剂量、吸收通量相关参数取值与产量损失的观察和分析结果的比较,找出更为合理的农作物臭氧风险评估阈值。结果表明:随着通量阈值Y[0~11 nmol O_3·m^(-2)PLA·s^(-1)(PLA:projected leaf area,投影叶面积)]和暴露浓度阈值X(0~50 n L·L^(-1))的增加,回归分析R^2值逐渐增加,当Y为11 nmol O_3m^(-2)PLA·s^(-1)和X为50 n L·L^(-1)时,气孔臭氧吸收通量POD11和累积暴露剂量AOT50与水稻相对产量的相关性最大,当通量阈值Y为8~13 nmol O_3·m^(-2)PLA·s^(-1)和暴露阈值X为46~58 n L·L^(-1)时,可获得较高的R^2值取值范围,分别为0.70~0.75和0.70~0.745。参考文献发现,目前地表臭氧污染可能引起的水稻产量损失范围为5%~8%,对照圈中POD9~10和AOT40~45产量损失的预测值亦在这区间,但前者R^2值(0.73~0.74)明显高于后者R^2值(0.64~0.69),表明基于气孔臭氧通量的评价指标能更好地反映水稻产量的变化。通过进一步分析发现,当通量阈值Y为9 nmol O_3·m^(-2)PLA·s^(-1)时,能更准确地评估水稻产量损失,且其R^2值(0.73)高于通量指标POD6(0.57)。以上研究结果表明,通量指标POD9更适合评估亚热带地区O_3污染对水稻作物的影响。

水稻(Oryza sativa L·)捕光叶绿素a/b结合蛋白基因全长cDNA的克隆和特性分析

根据捕光叶绿素a／b结合蛋白基因（cab）家族中的保守序列设计PCR引物，扩增出的约310bpcDNA小片段为分子杂交探针，对构建的水稻cDNA文库进行杂交筛选，并结合PCR分析确定阳性克隆中cDNA片段的大小。通过对插入的cDNA片段最长的阳性克隆进行测序分析验证，克隆了水稻中1个cab基因全长cDNA，命名为cab-n8（GenBank登记号：AY445626）。cab-n8长为1128bp，从第55bp开始至789bp含有1个开放阅读框和1个终止密码子，编码244个氨基酸（GenBank登记号为AAR19267．1）；在3’端含有330bp的非编码区和Poly（A）18；在5’端有45bp的非编码区，在转录起始位点附近有TCA序列。通过序列分析，cab-n8编码的蛋白质在第54—216位包括典型的捕光叶绿素a／b结合蛋白功能域（chlorophll a／b binding domain）；在第141—158位含有无名指结构功能域（ring finger structure domain），该位点可能与捕光叶绿素结合蛋白与叶绿素a／b的结合有关；在第194—231位含有甘油醛-3-磷酸脱氢酶C端功能域（C-terminal domain of glyceraldehyde-3-phosphate dehydrogenase-like）。cab-n8编码的蛋白质预测的等电点和分子量分别为6．52和26955．80 Da。通过比较分析，cab-n8DNA序列（AY445626）和编码的氨基酸序列（AAR19267．1）与cab27DNA序列（AF094775．1）和编码的氨基酸序列（AAC67557．1）相似性最高，均为97％，显示cab家族基因在进化过程中是相当保守的。Northern blot分析表明，该基因在水稻叶和茎中表达没有差异，但光对其表达有明显的诱导促进作用。

Analysis of Genetic Relationship among Medicago sativa,Medicago falcate and Trigonella foenum-graecum Using ISSR

[Objective] This study aimed to analyze the genetic relationships among Medicago sativa,Medicago falcata and Trigonella foenum-graecum.[Method] ISSR technique was adopted to determine their genetic relationships.[Result] M.sativa,M.falcate and T.foenum-graecum had a broad genetic base.T.foenum-graecum shared closer relationship with M.falcata rather than M.sativa.The study on relationship between M.sativa and T.foenum-graecum was advantageous to identify disputable transition types.But a boundary should be found to identify species to be M.sativa or T.foenum-graecum.[Conclusion] This study will provide reference for identifying some disputable transition types.

逆境下水稻(Dryza sativa L.)rHsp90基因的克隆及功能分析

本研究中,利用差异显示法,在碳酸盐逆境下,从水稻(OryzasativaL.)根的cDNA文库中克隆得到了水稻热激蛋白90基因(rHsp90,GenBankAccessionNo.AB037681)。Northern杂交结果表明,在水稻根中,rHsp90基因的转录水平在包括盐(NaCl,NaHCO3和Na2CO3),PEG,高pH(pH8.0和pH11.0)以及热激(50℃)逆境下,都受到了不同程度的诱导。同时,适量表达rHsp90基因的酵母(Saccharomycescerevisiae)在各种盐逆境以及热激逆境中,生长状态要好于对照。对转水稻rHsp90基因烟草的抗盐(NaCl,NaHCO3)分析表明,转基因烟草的生长势要好于野生型烟草。通过以上研究表明,水稻rHsp90基因与逆境之间具有一定的应答关系,并在植物适应环境逆境过程中起着重要的作用。

不同遗传背景及环境中水稻(Oryza sativa L.)穗长的QTLs和上位性分析

以粳稻Azucena为父本与舢稻IR64杂交发展的一双单倍体（DH）群体，与籼稻IR1552杂交发展的一重组自交系（RI）群体为材料，应用分子标记图谱对2个群体在大田和盆栽2个环境下的穗长进行QTLs及上位性效应分析。DH群体中共检测到6个穗长QTLs，位于第1、4条染色体上的3个QTLs，在2个环境中稳定表达，未检测到上位性效应，加性效应为穗长遗传主效应。R1群体中，共检测到3个穗长QTLs及6对互作效应位点，位于策4条染色体上的1个QTL及位于第1、12条染色体上的2个互作位点在2个环境中稳定表达，上位性效应表现为遗传主效应。在2个群体中均检测到的与穗长相关的1个QTL位于第4条染色体RG163～RZ23区间内，遗传正效应等位基因来源于Azucena；位于第1条染色体与RG323连锁的位点在DH群体中表现为1个QTL，但在RI群体中表现为互作位点。

Advances in Physiological-biochemical and Genetic Mechanisms of Seed Aging in Rice(Oryza sativa L.)

Reasons causing or accelerating seed aging are mainly damage of mem- branes, DNA and proteins, decline of protein synthesis capacity and excessive ac- cumulation of reactive oxygen species. With the application of natural aging or artifi- cial aging methods, it was reported that quantitative trait loci （QTLs） of seed stora- bility in rice were widely distributed on the chromosomes except the 10th chromo- some. In this paper, we reviewed the progresses in the research on physiological- biochemical and genetic mechanisms of seed aging, and analyzed the existing problems and developing prospect in molecular breeding of rice with improved seed storability, in order to provide reference for the basic research and genetic improve- ment of rice seed storabUity.

低钾胁迫对水稻(Oryza sativa L.)化感潜力变化的影响

研究以国际公认的化感水稻PI312777和非化感水稻Lemont为供体,稗草(Echinochloa crus-galli L.)为受体,采用稻/稗共培体系,研究低钾胁迫对水稻化感潜力变化的影响及其机制。受体稗草的形态指标分析结果表明,低钾胁迫促使化感水稻PI312777对共培稗草的根长、株高和干重的抑制率均升高,增幅远大于非化感水稻Lemont。受体稗草生理生化指标分析结果表明,低钾胁迫下化感与非化感水稻对受体稗草保护酶系(SOD、POD、CAT)及根系活力的抑制作用增强,但化感水稻PI312777比非化感水稻Lemont的抑制程度大,且达极显著差异。实时荧光定量PCR分析结果表明,低钾胁迫下,化感水稻PI312777根部与叶部中酚类代谢的关键酶——苯丙氨酸解氨酶、肉桂酸-4-羟化酶、羟化酶、O-甲基转移酶的基因均上调表达,而非化感水稻根部相应酶均下调表达,叶部除苯丙氨酸解氨酶上调,其余酶也下调表达。而萜类代谢途径关键酶——HMG-CoA还原酶、角鲨烯合酶、单萜烯环化酶、倍半萜烯环化酶、二萜烯环化酶的基因,在两种水稻根部中呈现出相同或相似的表达方式(上调或下调),即HMG-CoA还原酶上调表达,角鲨烯合酶、单萜烯环化酶、倍半萜烯环化酶、二萜烯环化酶下调表达;而在水稻叶部,非化感水稻Lmont相应酶基因表达方式仍然不变,化感水稻PI312777除了角鲨烯合酶下调表达,其余4个酶均上调表达。水稻根系分泌物中酚类物质的HPLC分析结果表明,低钾胁迫下,化感水稻PI312777根系分泌物中,所检出的酚酸类物质总量是正常营养条件下的2.30倍,而非化感水稻Lemont则是正常营养条件下的0.91倍。综合分析认为低钾胁迫下,化感水稻PI312777抑草能力增强主要是由于酚类代谢途径关键酶基因表达上调,导致酚类代谢途径旺盛,分泌出更多的酚类物质,进而破坏受体稗草保护酶系统,抑制了稗草的正常生长。