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Rice is an important crop that provides nutrition and energy to the global population. Therefore, increasing rice yield is the ultimate goal of rice breeding. Rice leaf is the main photosynthesis organ. Leaf shape affects the efficiency of light capture and energy conversion. Appropriate leaf shape can improve plant photosynthesis efficiency and increase plant yield Tsukaya, ; Micol, Many studies have characterized genes which control the rolling and width of rice leaves. The process of leaf development in rice has been divided into four parts: leaf primordia formation, polarity establishment, tissue differentiation and leaf extension Fan and Liang, Establishment of polarity is an important process that affects leaf morphology by regulating the adaxial inward and abaxial outward rolling of leaves Fan and Liang, Research in Arabidopsis thaliana and maize showed that transcription factors and small RNAs are involved in regulation during establishment and maintenance of leaf adaxial—abaxial axis polarities Moon and Hake, There is substantial evidence that defects in the establishment of polarity have a major impact on leaf rolling.
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Recently, a number of genes involved in the establishment of leaf polarity in rice have been identified. ADL1 gives rise to a plant-specific calpain-like cysteine proteinase which participates in leaf adaxial—abaxial axis maintenance, which the mutant showed abaxially rolled leaves Hibara et al. In addition to the establishment of polarity, the shape of bulliform cells also has an important role in rolling of leaves Alvarez et al.
Rolling-leaf 14 RL14 encodes a 2OG-Fe II oxygenase family protein which regulates curling of leaves by affecting the formation of secondary walls. Mutants with an altered secondary wall composition exhibit changes in the shape of the bulliform cells, which affects water transport in the leaf Fang et al. Cell division and expansion are essential phases in the conversion of leaf primordia to mature leaves Gonzalez et al. Many mutants showing abnormal leaf size have been characterized, caused by defects in cell division and cell expansion.
For instance, Slender Leaf 1 SLE1 encodes cellulose synthase-like D4, regulating cell proliferation during M phase and participated in cell wall formation, the mutant of which showed narrow and rolling leaves Li M. In the present study, we isolated and identified a narrow and rolled leaf mutant, nrl3. Compared with the wild-type, nrl3 showed darker green leaves at the tillering stage and with shorter panicles and longer, narrower seeds. Histological analysis showed that nrl3 had a decreased number of vascular bundles and defects of the abaxial sclerenchymatous cells which, respectively, caused leaf narrowed and rolling in rice.
In depth analysis of NRL3 can enhance our understanding of leaf morphogenesis and provides new genetic resources for improving rice. The nrl3 line was from a library of Oryza sativa subsp. The F 2 population for gene mapping was generated by crossing between nrl3 and tropical japonica rice variety D Leaf rolling index LRI was determined for the upper leaf by measuring L w the maximum width of the expanded leaf blade and L n the natural distance of the leaf blade margins at the same position.
Photosynthetic rate and transpiration rate were measured at the heading stage from 00 to 00 with a Li portable photosynthesis apparatus. Measurements of LRI, net photosynthetic rate and transpiration rates of wild-type and the nrl3 mutant were repeated at least three times, each replication used five independent plants.
To map the NRL3 locus, plants with narrow and rolling leaves were selected from the F 2 population. First, we used both parents and 20 F 2 individuals with the mutant phenotype for linkage analysis of NRL3. More than polymorphic SSR markers evenly distributed on the whole rice genome were employed. Then a further recessive individuals with the mutant phenotype were selected from the F 2 population to fine map the NRL3 locus.
The leaves of the wild-type and the nrl3 mutant at the heading stage were collected, fixed in 2. Then, the samples were dehydrated in a graded ethanol series, 20 min for each step, followed by substitution with isoamyl acetate. The samples were critical-point dried and sputter-coated with gold. The samples were observed and photographed using a scanning electron microscopy XL30, Philips, United States.
Total RNA was extracted from different plant tissues root, stem, leaf, leaf sheath, panicle, and seeds of wild-type and nrl3 using Trizol reagent Life Technologies. The rice actin gene Os03g was used as internal control. All the materials used for RNA extraction were from mixing three independent plants. These plasmids were introduced into Agrobacterium tumefaciens strain EHA Genotypes of the independent transgenic lines were determined by PCR amplification of the specific transgenic fragment all primers used for plasmid construction are listed in Supplementary Table S1.
The fusion plasmid was transiently co-expressed in rice protoplasts using polyethylene glycol according to the protocols described previously Chen et al. The free pAN vector was used as control. Fresh leaves of wild-type and nrl3 rice plants at heading stage were used to determine chlorophyll content according to the previous described method Wu et al. Aliquots of 0. A DU spectrophotometer Beckman Coulter, United States was used to measure absorption of the supernatant at and nm.
These plasmids were transiently expressed in tobacco leaves using A.
Primers used in this assay are listed in Supplementary Table S1. The mutant nrl3 was identified from a library produced using ethyl methanesulfonate EMS on an indica rice variety Zhongjiazao 17 YK The nrl3 plants exhibited narrow and rolled leaves over the whole duration of growth. They had darker green leaves at the tillering stage which became more obvious with plant growth Figure 1A and Supplementary Figures S5A,B.
Investigation of agronomic traits revealed no obvious differences in the plant height and effective tillers number between wild-type and nrl3 Supplementary Figures S1A,C , but panicle length was significantly decreased in nrl3 Figure 1B and Supplementary Figure S1B. Finally, the grain width and grain weight of nrl3 were significantly decreased Figure 1G and Supplementary Figure S1D , while the grain length of nrl3 was significantly increased Figures 1C,H compared with the wild-type.
Therefore, mutation in NRL3 leads to multiple changes in plant agronomic traits. Figure 1. Phenotype the nrl3 mutant. A Upper leaf of WT, nrl3 -1, and nrl3 B Panicle length of WT, nrl3 -1, and the nrl3 -2 mutant.
C Grain length of WT, nrl3 -1, and nrl3 Bar: 1 cm A—C. RNA was isolated from leaves at tillering stage of WT and nrl3 of three independent plants. F Leaf width of the flag leaf of WT and the nrl3 mutant plant of three independent plants. G Thousand-grain weight of WT and nrl3.ssh.fuelrats.com/la-comida-de-integracin-clculo-simple.php
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H Grain length of WT and nrl3. To explore the reasons for the narrow and rolled leaves in nrl3 mutant, we carried out an analysis of cross-sections in the flag leaf. Compared with the wild-type, the nrl3 had fewer large and small veins. There were on average only six large veins in the nrl3 mutant, half the number in the wild-type Figure 2A. Furthermore, in nrl3 mutant there were on average three small veins between each two neighboring large veins, compared to six in the wild-type Figure 2B. Observed the cross-sections, we found that the development of abaxial sclerenchymatous cells was defective in the region of some small veins in nrl3 mutant, although the adaxial sides were normal Figure 2C.
In addition, we found that the air cavity and parenchymal cell of the nrl3 leaves differed from the wild-type. The mutant displayed the number of parenchyma cells on the large veins was decreased Figure 2D. To confirm our results, we observed the abaxial side and adaxial side of the leaves by scanning electron microscopy SEM.
This showed defects in the sclerenchymatous cells on the abaxial side of the nrl3 leaves, while the adaxial side was similar to the wild-type Figures 2E,F. Figure 2. Cytological analysis of WT and nrl3. A—D Cross sections of leaves at the heading stage from WT, nrl3 -1, and nrl3 E,F Scanning electron microscopy of the adaxial and abaxial sides of WT, nrl3 -1, and nrl3 -2 leaves.
In order to identify the inheritance of NRL3 , map-based cloning was conducted using a F 2 population produced by crossing the nrl3 with D50 tropical japonica variety. According to the Rice Genome Annotation Project database 3 , there are 42 ORFs in this interval, which were selected for sequencing analysis. Figure 3. Map-based cloning of NRL3. B The leaf phenotype of knock-out transgenic plants CP. Bar: 1 cm. C The phenotype of overexpression transgenic plants OE. D,E Upper leaf width of knock-out transgenic plants D and overexpression transgenic plants E. F,G Upper leaf rolling in knock-out transgenic plants F and overexpression transgenic plants G.
H Expression levels of NRL3 in knock-out transgenic plants. I Expression level of NRL3 in overexpression transgenic plants. RNA was isolated from leaves at tillering stage of wild-type, nrl3 and transgenic plants. We found all of the over-expression plants were able to rescue the narrow and rolled leaf phenotype of nrl3 , with increased leaf width, decreased LRI, and a lighter green color Figures 3C,E,G,I.
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Protein sequence analysis showed NRL3 encoded a novel protein with unknown function. Phylogenetic analysis revealed that NRL3 protein may have a conserved function in both monocotyledons and dicotyledons Supplementary Figure S4. Quantitative real-time PCR analysis suggested that NRL3 was constitutively expressed in all tested organs, with the highest levels in leaf sheaths Figure 4A. To address these concerns, scientists have designed a highly sensitive test that can be used to establish the integrity of blood plasma and serum, the most common biosamples used in medical research.
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