为了研究一个水稻黄叶突变基因与叶绿素合成途径的关系及突变基因的作用机理，本研究以野生型作对照，结合半定量与实时定量PCR技术，对突变体茎和叶组织中叶绿素合成关键基因的RNA表达水平进行了分析。结果显示，在茎组织中，研究选取的8个基因在突变体和野生型中的表达均没有明显差别。而在叶组织中，突变体的YGL1和CHLI两个基因的表达量约为野生型的1.8倍，表达明显上调；CHLD基因的表达量约为野生型的0.6倍，表达明显下调；其余5个基因的表达没有明显差别。研究表明，突变基因能够调控叶绿素合成关键基因YGL1、CHLD和CHLI的表达，从而影响叶组织中叶绿素的合成，这为进一步研究突变基因对叶绿素合成的调控模式及其作用机理奠定了基础。

Chlorophyll (Chl) has unique and essential roles in photosynthetic light-harvesting and energy transduction, but its biosynthesis, accumulation and degradation is also associated with chloroplast development, photomorphogenesis and chloroplast-nuclear signaling. Biochemical analyses of the enzymatic steps paved the way to the identification of their encoding genes. Thus, important progress has been made in the recent elucidation of almost all genes involved in Chl biosynthesis and breakdown. In addition, analysis of mutants mainly in Arabidopsis, genetically engineered plants and the application of photo-reactive herbicides contributed to the genetic and regulatory characterization of the formation and breakdown of Chl. This review highlights recent progress in Chl metabolism indicating highly regulated pathways from the synthesis of precursors to Chl and its degradation to intermediates, which are not longer photochemically active.

水稻叶穗色泽突变体为解析不同器官叶绿素生物合成之间的内在联系提供了优良的遗传材料。本研究鉴定了1份白叶白穗突变体wlwp7（white leaf and white panicle 7）,分析了wlwp7的形态、生理和遗传特点。结果表明：wlwp7对低温敏感,当环境温度为20 ℃时苗期叶片白化,但温度升高至30 ℃后叶色正常;大田环境下wlwp7抽穗后颖壳白化,叶绿素含量降低至野生型的40.73%;除结实率较野生型T98B下降6.28%外,其他产量性状不受影响;遗传分析发现,wlwp7与T98B的正反杂交F₂群体中都未出现白叶绿穗和绿叶白穗重组单株,经卡方检测白叶白穗突变单株与绿叶绿穗野生型单株的理论分离比符合1∶3,表明白叶白穗性状受同一隐性核基因控制;利用BSA策略进一步将wlwp7定位在第3染色体上一个280 kb的区域内,该区域未有已报道的白叶白穗基因。本研究发现了wlwp7同时控制叶部和穗部叶绿素合成,精细定位结果为最终克隆wlwp7奠定了基础。

【目的】对水稻类病斑突变体的研究有助于解析其与植物生长和防御反应的关系。【方法】本研究在粳稻品系FI135胚培养过程中获得了1个类病斑突变体lmm7(lesion mimic mutant 7)。通过对其进行系统的表型鉴定、农艺性状考查、超微结构观察、生理学特性分析，阐明LMM7基因对植物生长的调控。通过病原菌抗性鉴定，明确lmm7对植物防御反应的影响。利用9311B与突变体lmm7杂交所得F₂群体对该突变体进行了遗传分析和基因精细定位。【结果】该突变体苗期表型正常，分蘖初期，植株基部叶片从叶尖开始不断出现褐色斑点，并向整株扩散，且斑点数目随植株生长不断增加。与野生型相比，突变体的株高、穗长、有效穗数、每穗粒数、结实率及剑叶长宽都显著降低，但籽粒性状和抽穗期没有显著性差异。遮光处理表明，突变体lmm7的表型受到光照诱导，抽穗期突变体lmm7叶肉细胞严重失绿，光合色素含量显著降低。组织化学分析表明，突变体病斑处的H₂O₂含量显著升高。透射电镜观察结果表明，突变体lmm7叶肉细胞的叶绿体数目减少，叶绿体类囊体片层结构严重受损，细胞器肿胀解体，并出现大量嗜锇小体，同时病斑内部和周围区域积累了大量的ROS。抗性鉴定结果显示突变体lmm7稻瘟病抗性水平显著高于野生型。遗传分析表明lmm7的突变表型受单个隐性基因控制。利用图位克隆的方法，目的基因被定位于水稻第7染色体短臂两InDel标记7B35和7B43之间，区间范围约260 kb。测序结果表明该区间内候选基因LOC_Os07g0203700第2891位碱基T发生了单碱基缺失，导致后续移码突变及翻译提前终止。【结论】lmm7与spl5互为等位基因，其突变抑制了植株的生长，同时增强了对稻瘟病的抗性。

A chloroplast signal recognition particle (SRP) that is related to the SRP involved in secretion in bacteria and eukaryotic cells is used for the insertion of light-harvesting chlorophyll proteins (LHCPs) into the thylakoid membranes. A conserved component of the SRP mechanism is a membrane-bound SRP receptor, denoted FtsY in bacteria. Plant genomes encode FtsY homologs that are targeted to the chloroplast (cpFtsY). To investigate the in vivo roles of cpFtsY, we characterized maize cpFtsY and maize mutants having a Mu transposon insertion in the corresponding gene (chloroplast SRP receptor1, or csr1). Maize cpFtsY accumulates to much higher levels in leaf tissue than in roots and stems. Interestingly, it is present at similar levels in etiolated and green leaf tissue and was found to bind the prolamellar bodies of etioplasts. A null cpFtsY mutant, csr1-1, showed a substantial loss of leaf chlorophyll, whereas a "leaky" allele, csr1-3, conditioned a more moderate chlorophyll deficiency. Both alleles caused the loss of various LHCPs and the thylakoid-bound photosynthetic enzyme complexes and were seedling lethal. By contrast, levels of the membrane-bound components of the thylakoid protein transport machineries were not altered. The thylakoid membranes in csr1-1 chloroplasts were unstacked and reduced in abundance, but the prolamellar bodies in mutant etioplasts appeared normal. These results demonstrate the essentiality of cpFtsY for the biogenesis not only of the LHCPs but also for the assembly of the other membrane-bound components of the photosynthetic apparatus.

为探究甜瓜皮色性状的遗传规律，定位目标性状关联的遗传位点，选用黄皮材料B432 和绿皮材料B168、B421 为亲本，构建6 世代遗传群体(P1、P2、F1、F2、BC1P1、BC1P2)，用于分析甜瓜皮色性状的遗传规律；同时，利用BSA-seq 和全基因组重测序技术，定位控制甜瓜皮色的基因。结果表明，甜瓜皮色由2对基因控制，其中绿色对白色具有显性上位性效应，白色对黄色为显性。同时，将皮色相关基因分别定位于4 号染色体和10 号染色体的0.02~5.7 Mb和0.08~9.5 Mb区间。试验初步定位了控制甜瓜皮色的基因，为后续进行基因精细定位提供依据，为开展甜瓜皮色的分子标记辅助选择奠定基础。

温度是影响水稻生长发育的一个重要因素,由温度引起水稻叶色改变的一类突变体统称为水稻温敏感叶色突变体。探讨温度影响水稻叶色的机理,对促进水稻遗传改良与高产育种具有重要意义。对已发掘的水稻温敏感突变体在温度对突变体的表型影响、基因定位及克隆、分子作用机理和育种利用及其研究进展等方面进行了分类讨论。

光温敏不育系的育性因易受光温条件影响而出现波动,导致种子纯度不够,是水稻生产上常见的问题。本研究对1个水稻黄叶不育系突变体H08S进行温度敏感性分析和叶绿体超微结构观察,同时通过构建分离群体进行突变基因的遗传模式分析。结果表明,突变体H08S的表型受温度影响,为低温表达型叶色突变体,且其叶绿体结构出现异常,表现类囊体的片层结构减少,说明H08S基因的突变影响叶绿体的正常发育。突变体H08S分别与‘日本晴’、‘02428’构建F₂群体和BC₁F₁群体,观察并统计群体植株叶色表型的分离情况,并进行卡方检验,结果表明该突变性状受1对隐性单基因控制。

The rice zebra mutant TCM248 is a single recessive mutant. This mutant develops transverse-striped leaves with green and white sectors under alternate light/dark growth conditions. Mutants that were grown under a higher light intensity during the light period showed a more intense striped phenotype. The white tissues contained abnormal chloroplasts with few internal membrane structures, while the green tissues in the mutants contained normal chloroplasts. The white tissue contained only trace amounts of Chls and carotenoids, and mRNA accumulation of nuclear genes encoding chloroplast proteins (rbcS, cab) was strongly suppressed compared to that in the wild type plants. A series of growth condition shift experiments demonstrated that the mutant displayed the striped phenotype only if it was exposed to the alternate light/dark growth conditions during a limited stage of early leaf development. These data suggest that the zebra gene is involved in the acquisition of photoprotective capacity of the plants and that this gene functions at an early stage of chloroplast differentiation.

Geranylgeranyl reductase (CHL P) catalyzes the reduction of geranylgeranyl diphosphate to phytyl diphosphate, and provides phytol for both Chlorophyll (Chl) and tocopherol synthesis. In this study, we isolated a yellow-green leaf mutant, 502ys, in rice (Oryza sativa). The mutant exhibited reduced level of Chls, arrested development of chloroplasts, and retarded growth rate. The phenotype of the 502ys mutant was controlled by by a recessive mutation in a nuclear gene on the long arm of rice chromosome 2. Map-based cloning of the mutant resulted in the identification of an OsChl P gene (LOC_Os02g51080). In the 502ys mutant, a single base pair mutation was detected at residue 1279 in DNA sequence of the gene, resulting in an amino acid change (Gly-206 to Ser) in the encoded protein. HPLC analysis of Chls indicated that the majority of Chl molecules are conjugated with an unsaturated geranylgeraniol side chain, in addition to small amount of normal Chls in the mutant. Furthermore, the mutant phenotype was complemented by transformation with the wild-type gene. Therefore, this study has confirmed the 502ys mutant resulted from a single base pair mutation in OsChl P gene.

Chlorophyll (Chl) synthase catalyzes esterification of chlorophyllide to complete the last step of Chl biosynthesis. Although the Chl synthases and the corresponding genes from various organisms have been well characterized, Chl synthase mutants have not yet been reported in higher plants. In this study, a rice (Oryza Sativa) Chl-deficient mutant, yellow-green leaf1 (ygl1), was isolated, which showed yellow-green leaves in young plants with decreased Chl synthesis, increased level of tetrapyrrole intermediates, and delayed chloroplast development. Genetic analysis demonstrated that the phenotype of ygl1 was caused by a recessive mutation in a nuclear gene. The ygl1 locus was mapped to chromosome 5 and isolated by map-based cloning. Sequence analysis revealed that it encodes the Chl synthase and its identity was verified by transgenic complementation. A missense mutation was found in a highly conserved residue of YGL1 in the ygl1 mutant, resulting in reduction of the enzymatic activity. YGL1 is constitutively expressed in all tissues, and its expression is not significantly affected in the ygl1 mutant. Interestingly, the mRNA expression of the cab1R gene encoding the Chl a/b-binding protein was severely suppressed in the ygl1 mutant. Moreover, the expression of some nuclear genes associated with Chl biosynthesis or chloroplast development was also affected in ygl1 seedlings. These results indicate that the expression of nuclear genes encoding various chloroplast proteins might be feedback regulated by the level of Chl or Chl precursors.

Pentatricopeptide repeat (PPR) proteins comprise a large family in higher plants and modulate organellar gene expression by participating in various aspects of organellar RNA metabolism. In rice, the family contains 477 members, and the majority of their functions remain unclear. In this study, we isolated and characterized a rice mutant, white stripe leaf (wsl), which displays chlorotic striations early in development. Map-based cloning revealed that WSL encodes a newly identified rice PPR protein which targets the chloroplasts. In wsl mutants, PEP-dependent plastid gene expression was significantly down-regulated, and plastid rRNAs and translation products accumulate to very low levels. Consistently with the observations, wsl shows a strong defect in the splicing of chloroplast transcript rpl2, resulting in aberrant transcript accumulation and its product reduction in the mutant. The wsl shows enhanced sensitivity to ABA, salinity, and sugar, and it accumulates more H2O2 than wild-type. These results suggest the reduced translation efficiency may affect the response of the mutant to abiotic stress. © The Author 2014. Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS.

钾离子参与植物多个生理代谢过程，能不同程度地缓解植物受到的盐胁迫，促进植物生长发育。为了全面了解外源钾对盐胁迫下植物生长的影响，本研究归纳了盐胁迫对植物生长代谢的影响，钾在植物体内的生理作用以及外源钾对盐胁迫下植物生长生理特征的影响；分析了钾对盐胁迫下植物的生长发育、光合荧光特性、渗透物质及抗氧化酶活性、体内水分状况及离子分布的影响。针对当前钾离子缓解植物盐胁迫的分子机制及应用研究较少的问题，建议在今后的研究着重从以下两方面开展：（1）明确盐胁迫下植物体内钾离子转运机制、信号转导和相关基因的调控表达；（2）开展盐碱地肥料长期定位研究并研发可以提高植物耐盐性的新型钾肥。通过以上研究的开展，可为今后利用钾提高植物耐盐性以及盐渍土壤的改良提供解决方案。

The main objective of this study was to identify the genes causing etiolation in a rice mutant, the thylakoids of which were scattered. Three populations were employed to map the genes for etiolation using bulked segregant analysis. Genetic analysis confirmed that etiolation was controlled by two recessive genes, et11 and et12, which were fine mapped to an approximately 147-kb region and an approximately 209-kb region on the short arms of chromosomes 11 and 12, respectively. Both regions were within the duplicated segments on chromosomes 11 and 12. They possessed a highly similar sequence of 38 kb at the locations of a pair of duplicated genes with protein sequences very similar to that of HCF152 in Arabidopsis that are required for the processing of chloroplast RNA. These genes are likely the candidates for et11 and et12. Expression profiling was used to compare the expression patterns of paralogs in the duplicated segments. Expression profiling indicated that the duplicated segments had been undergone concerted evolution, and a large number of the paralogs within the duplicated segments were functionally redundant like et11 and et12.

通过甲基磺酸乙酯(EMS)诱变晚粳稻品种秀水09,获得了1个稳定遗传的全生育期黄绿叶突变体Ygl,遗传分析表明该突变性状由1对隐性核基因控制。利用突变体与籼稻品种珍汕97杂交,构建F₂群体对突变基因进行定位,发现目的基因与第11号染色体上的SSR标记RM2459连锁,在该标记附近发展了14对InDel标记,将突变基因定位在约82kb区间内。通过在线最新水稻注释系统的基因功能预测分析,寻找候选基因,经测序发现突变体发生单碱基突变。

Rice heme oxygenase 2 (OsHO2) mutants are chlorophyll deficient with distinct tetrapyrrole metabolite and transcript profiles, suggesting a potential regulatory role of the stromal-localized OsHO2 in tetrapyrrole biosynthesis. In plants, heme oxygenases (HOs) are classified into the subfamilies HO1 and HO2. HO1 are highly conserved plastid enzymes required for synthesizing the chromophore in phytochromes which mediate a number of light-regulated responses. However, the physiological and biochemical functions of HO2, which are distantly related to HO1, are not well understood, especially in crop plants. From a population of (60)Coγ-irradiated rice mutants, we identified the ylc2 (young leaf chlorosis 2) mutant which displays a chlorosis phenotype in seedlings with substantially reduced chlorophyll content. Normal leaf pigmentation is gradually restored in older plants while newly emerged leaves remain yellow. Transmission electron microscopy further revealed defective chloroplast structures in the ylc2 seedlings. Map-based cloning located the OsYLC2 gene on chromosome 3 and it encodes the OsHO2 protein. The gene identification was confirmed by complementation and T-DNA mutant analyses. Subcellular localization and chloroplast fractionation experiments indicated that OsHO2 resides in the stroma. However, recombinant enzyme assay demonstrated that OsHO2 is not a functional HO enzyme. Analysis of tetrapyrrole metabolites revealed the reduced levels of most chlorophyll and phytochromobilin precursors in the ylc2 mutant. On the other hand, elevated accumulation of 5-aminolevulinic acid and Mg-protoporphyrin IX was observed. These unique metabolite changes are accompanied by consistent changes in the expression levels of the corresponding tetrapyrrole biosynthesis genes. Taken together, our work suggests that OsHO2 has a potential regulatory role for tetrapyrrole biosynthesis in rice.

在水稻品种南粳41中发现了一个黄绿叶自然突变体,经过多代连续自交形成了稳定的突变系,命名为ygl11(t),ygl11(t)整个生育期叶片都表现为黄绿色。对苗期、分蘖盛期、齐穗期突变体和野生型的叶绿素含量进行测定,ygl11(t) 的叶绿素含量是野生型的45.7%~74.7%,叶绿素a 含量是野生型的55.2%~87.5%,叶绿素b含量是野生型的12.5%~25.3%,ygl11(t) 的类胡萝卜素的含量是野生型的62.3%~97.0%。ygl11(t)在分蘖盛期的净光合速率显著高于野生型,花后10 d,ygl11(t)的净光合速率比野生型略低。对突变体叶片中叶绿体的超微结构进行观察,发现突变体叶绿体内的类囊体基粒片层数目减少且严重扭曲变形。遗传分析表明,ygl11(t)叶色性状受1对隐性核基因控制。利用SSR分子标记将YGL11(t)初步定位在水稻第10染色体的长臂上,进一步利用新开发的InDel和CAPS标记将YGL11(t)定位在58.1 kb的物理距离内。对该区段内存在的开放阅读框进行序列分析,发现突变体ygl11(t) 中编码叶绿素a氧化酶(chlorophyll a oxygenase 1)基因(OsCAO 1) 的第9个外显子存在2个碱基缺失,从而导致提前出现终止密码子,初步分析OsCAO1即为YGL11(t)的候选基因。