Rice Crinkly4 receptor-like kinase positively regulates culm elongation and amino acid K532 is not essential for its kinase activity

Receptor-like kinases (RLKs) play important roles in multiple aspects of plant growth and development. As a member of the TNFR-like RLK subfamily, rice Crinkly4 (OsCR4) functions mainly in epidermal cell differentiation in many organs. Here we show that in addition to its essential role in epidermal cell differentiation in the palea and lemma, OsCR4 positively regulates rice culm elongation, similar to maize CR4. Although OsCR4 is an active kinase, like CR4 in maize and ACR4 in Arabidopsis, the conserved amino acid K532 in OsCR4 is not essential for its kinase activity in vitro. Whether other conserved amino acids are required for its kinase activity and the relationship between its activity and function in plant development remain to be investigated.     

一个水稻内颖退化突变体的形态特征及基因的精确定位

水稻产量和品质受花器官发育的直接影响,因此对水稻颖花发育机理的研究将有助于水稻产量提高和品质的改良。文章利用60Coγ射线辐照亲本8PW33(籼稻背景)获得一个性状能稳定遗传的内颖退化突变体(编号:MU102),并对其农艺性状和花器官进行了观察和分析。结果显示,相对于野生型,该突变体的株高、每穗总粒数及剑叶宽均显著增加,而结实率则显著降低,差异均达显著水平。解剖镜下观察表明,该突变体内颖退化,外颖弯曲呈现镰刀状,其余器官与野生型表型基本一致。扫描电镜观察显示,突变体与野生型叶片维管束的结构组成以及外颖表皮细胞组成、排列均正常,没有明显差异;与野生型相比,突变体内颖表皮细胞排列较为紧密,推测可能是内颖收缩退化导致的。遗传分析显示该突变性状是由隐性单基因控制,并命名为pd2。利用实验室现有的SSR分子标记将PD2基因定位于水稻第9号染色体上,通过进一步扩大群体和开发新的Indel标记,将PD2基因定位在2个Indel标记之间,两者间的物理距离大约是82 kb。在该物理区间内有一个已经克隆的内颖发育基因REP1,经过测序和比对分析,推测REP1与PD2为等位基因。     

Ectopic expression of <Emphasis Type="Italic">OsMADS1</Emphasis> caused dwarfism and spikelet alteration in rice

In rice, an E-class gene, OsMADS1, acts to specify the identities of the lemma and palea. In this study, the OsMADS1 gene with a CaMV35S promoter was transformed into a japonica cultivar, Zhonghua 11. All transgenic plants successfully showed similar phenotypes, including dwarfism, distorted panicles, decreased numbers of branches and spikelets, and elongated sterile lemma. Histological analysis showed that the elongated sterile lemma developed with silicified epidermal and sclerenchymal cells, which were lacking in the wild-type sterile lemma, suggesting that the elongated sterile lemma had assumed the identity of the lemma or palea. Some marker genes were subjected to a detailed analysis of the distribution of their expression among the lemma, palea and sterile lemma. DROOPING LEAF (DL) and OsMADS6 genes were only expressed in the normal lemma or palea, respectively. In the elongated sterile lemma, a high level of DL gene expression was detected, while no expression of OsMADS6 was found, implying that the sterile lemma transformed into the lemma but not the palea. These results provide clues to elucidate the mechanism of evolution from lemma to sterile lemma in rice. qPCR analysis also suggested that the ectopic expression of OsMADS1 induced abnormal brassinosteroid and gibberellin acid activation, and then resulted in developmental defects in the stem and panicle.     

Characterization of an abiotic stress-inducible dehydrin gene, OsDhn1, in rice (Oryza sativa L.)

A full-length 1.1 kb cDNA, designated Oryza sativa Dehydrin 1 (OsDhn1), was isolated from the seed coat of rice. The deduced protein is hydrophilic and has three K-type and one S-type motifs (SK3-type), indicating that OsDhn1 belongs to the acidic dehydrin family, which includes wheat WCOR410 and Arabidopsis COR47. Expression of OsDhn1 was strongly induced by low temperature as well as by drought. Induction of OsDhn1 by cold stress was clearcut in the roots of seedlings and the epidermis of palea and lemma. OsDhn1 was also up-regulated in UBI::CBF1/DREB1b transgenic plants indicating that it is regulated by the CBF/DREB stress signaling pathway.     

Clearing, cuticle removal, and staining for the fertile bracts (lemmas and paleas) of grass anthoecia.

The epidermis of the bracts enclosing the flower of grasses contains epidermal cell patterns which are indicative of phylogenetic and systematic relationships among taxa. Treating the heavily cutinized anthoecial bracts (fertile lemma and palea) with 10% NaOH results in the removal of sufficient cuticle to allow examination of the cells of the epidermis. After clearing and removal of the cuticle, the bracts are bleached, washed, dehydrated, and if studied by light microscopy, stained in 2% chlorazol black E and mounted in Diaphane; or, if studied by scanning electron microscopy, dried by the critical-point method and either left uncoated or coated with a film of various conductive metals.     

Microscopic Observation on the Development of Puccinia striiformis in the Spike and Stem of Wheat

The majority of germ tubes of the pathotype CYR32 of Puccinia striiformis f.sp. tritici formed on the surface of spike organs of the susceptible wheat cv. Suwon 11 penetrated through the stomatal pore, only a few germ tubes formed small appressoria over the stomata. In the lemma, palea and glume, the stripe rust fungus spread between the parenchyma cells close to the inner epidermal layer, but the fungus did not develop between the thick‐walled cells near the outer epidermal layer of these organs. In the awn and stem, spread of the stripe rust was confined to the intercellular spaces of the chlorophyll parenchyma, beneath the invaded stomatal pore of the epidermis and the urediniospores to be released disrupted the epidermis. In the caryopsis, the spread of hyphae was restricted to the intercellular spaces of the pericarp cells.     

Clearing, Cuticle Removal, And Staining For The Fertile Bracts (Lemmas And Paleas) Of Grass Anthoecia

The epidermis of the bracts enclosing the flower of grasses contains epidermal cell patterns which are indicative of phylogenetic and systematic relationships among taxa. Treating the heavily cutinized anthoecial bracts (fertile lemma and palea) with 10% NaOH results in the removal of sufficient cuticle to allow examination of the cells of the epidermis. After clearing and removal of the cuticle, the bracts are bleached, washed, dehydrated, and if studied by light microscopy, stained in 2 % chlorazol black E and mounted in Diaphane; or, if studied by scanning electron microscopy, dried by the critical-point method and either left uncoated or coated with a film of various conductive metals.     

OsNRAMP5, a major player for constitutive iron and manganese uptake in rice

Manganese (Mn) and iron (Fe) are essential mineral micronutrients for plants and their deficiency and or toxicity represents a serious agricultural problem. In rice the information about genes involved in Mn uptake from soil is scarce. Recently, we showed that OsNRAMP5 is a plasma membrane protein involved in Mn and Fe transport. The concentration of Mn in roots, shoots and xylem sap of OsNRAMP5 RNAi (OsNRAMP5i) plants was significantly reduced compared with WT plants. The expression of OsNRAMP5 is not controlled by Fe deficiency in root and was also observed in pistil, ovary, lemma and palea. These data show that rice would utilize OsNRAMP5 for constitutive Fe and Mn uptake, while OsNRAMP5 would also play a role in Fe and Mn transport during flowering and seed development.     

ELE restrains empty glumes from developing into lemmas

Although there is evident homology among reproductive organs when comparing Poaceae(grass)and eudicots,the identity of grass specific organs,such as lodicules,palea,lemma,and glumes has been the subject of a vast and largely inconclusive discussion.Here we provide some direct evidence to support the idea that the empty glumes of rice(Oryza sativa)are counterparts of lemmas.We show that the development of empty glumes is regulated by ELE(elongated empty glume),which belongs to a plant specific novel gene family.Mutations at the ELE locus cause elongated empty glumes,which mimic the lemmas and have the epidermal morphology of lemmas with four or five vascular bundles.As a nuclear-localized gene,ELE is specifically expressed at the empty glumes of immature spikelets,and its ectopic expression causes many floral development defects,including lemma-like palea,extra palea-like structures,elongated lodicules,extra stamens and stigmas.Our result suggests that empty glumes are lemmas of the sterile florets located at the lateral side of the rice spikelet,and ELE acts as a regulator restraining its growth to maintain its small size in wild-type plants.     

水稻内颖畸形或缺失基因OsAPP1的图位克隆及表达分析

在育种基地材料中发现一株内颖畸形或缺失(abnormal or absent palea)突变体,将其命名为app1。该突变体在营养生长时期发育正常,但抽穗后突变体表现出内颖畸形(比外稃短导致颖壳不闭合,或者出现两个内稃)或缺失,其花粉育性为55.52%,结实率为6.48%,千粒重为10.811 g,种子发芽率为55.21%。以突变体app1与日本晴杂交构建了F1和F2群体,F1颖壳表型正常,F2群体出现内颖畸形和正常表型分离,内颖正常和突变表型分离比例为3∶1,表明app1内颖突变表型由单隐性核基因控制。以F2为分离群体,将app1精细定位于第3染色体上,位于分子标记ID4231和ID4246之间,遗传距离1.3 cM,对应物理距离为13.2 kb。该区段内完全包含1个开放阅读框,包含两个部分开放阅读框,经过测序分析发现候选基因LOC_Os03g11614启动子区发生点突变和245 bp缺失,qRT-PCR分析证实LOC_Os03g11614为OsAPP1基因。已有报道LOC_Os03g11614编码OsMADS1,是调控水稻花器官发育的重要明星基因,其不同位置的突变可以导致叶状颖壳和不育、以及控制籽粒大小。与3000份水稻种子资源SNP/Indel变异类型对比分析发现,突变体app1启动子的突变完全不同于现已OsMADS1研究报道突变类型,且与数据库中的自然突变类型多数不同。因此,本研究发现的app1突变体,是以往报道中从未出现的OsMADS1启动子发生突变的新型突变,且该类突变导致了其降低表达量,并产生了不同于前人研究的新表型,这为深入研究OsMADS1基因在水稻花器官发育中的功能提供了新的种质资源和思路。     

Ectopic expression of OsMADS3, a rice ortholog of AGAMOUS, caused a homeotic transformation of lodicules to stamens in transgenic rice plants

In order to clarify the evolutionary relationship of floral organs between grasses and dicots, we expressed OsMADS3, a rice (Oryza sativa L.) AGAMOUS(AG) ortholog, in rice plants under the control of an Actin1 promoter. As a consequence of the ectopic expression of the OsMADS3, lodicules were homeotically transformed into stamens. In total, the transformation of lodicules to staminoid organs was observed in 18 out of 26 independent transgenic lines. In contrast to the almost complete transformation occurring in lodicules, none of the transgenic plants exhibited any morphological alterations in the palea or the lemma. Our results confirmed the prediction that the lodicule is an equivalent of a dicot petal and that the ABC model can be applied to rice at least for organ specification in lodicules and stamens.     

Storage-protein Deposition in the Developing Rice Caryopsis in Relation to the Transport Tissues

The developing caryopsis of rice (Oryza sativa L.) was examinedhistologically at successive stages of grain-filling in orderto identify the factors which determine the distribution ofstorage protein in the endosperm, and which terminate the depositionof endosperm protein. The storage protein was deposited at theperiphery of the endosperm, and this distribution was apparentlycaused by the radial pattern of cell development in the endosperm,and by the proximity of the peripheral endosperm cells to thenucellar epidermis. The nucellar epidermis directly surroundsthe endosperm and functions as the pathway for amino acid transportto the endosperm. During the later stages of caryopsis developmentthe nucellar epidermis became compressed by being ‘sandwiched’between the expanding endosperm and the rigid hull (the tightlylocked palea and lemma) which encloses the caryopsis. It isproposed that this compression of the nucellar epidermis blocksthe supply of amino acids to the endosperm and thereby terminatesthe deposition of storage protein in the rice grain. Oryza sativa, rice, caryopsis (development), endosperm, grain filling, nucellar epidermis, storage protein