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A rice floral mutant was obtained from a japonica variety Zhonghua 11, which was characterized with the phenotype of more stamens, more pistils and early flowering. Genetic analysis showed that the mutant phenotype was controlled by a single recessive gene, which was designed as floral organ number 5 (fon5). To map fon5, an F2 population was derive...
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We have analyzed a lax mutant that exhibits altered panicle architecture in rice. The primary and secondary rachis-branches are normally initiated
and each branch ends in a terminal spikelet, but all the lateral spikelets are absent and the terminal spikelet displays variegated
structures in the mutant. An F2 population from the cross between the l...
Grain shape is one of the most important and complex traits determining the grain yield in rice. In this study, we discovered two rice mutants with defective shape spikelets, designated as psh1-1/2 (pepper-shaped husk 1-1/2), which were both isolated from the tissue-culture-regenerated plants of indica cultivar Minghui 86. The two mutants showed th...
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... While the approximate chromosomal positions of FON5 and FON6 have been determined, their exact gene-related information and biological functions remain unknown. The fon1, fon2, fon5, and fon7 mutants were generated by chemical mutagenesis, whereas fon3 was found to exist as a spontaneous mutant in the Gu-Guang-Huang farm line [17,[28][29][30][31]. The fon5 and fon7 mutants exhibit similar phenotypes, i.e., increased stamen and pistil numbers and homeotic conversion of stamens and pistils (Fig 1j-1o) [31]. ...
... The fon1, fon2, fon5, and fon7 mutants were generated by chemical mutagenesis, whereas fon3 was found to exist as a spontaneous mutant in the Gu-Guang-Huang farm line [17,[28][29][30][31]. The fon5 and fon7 mutants exhibit similar phenotypes, i.e., increased stamen and pistil numbers and homeotic conversion of stamens and pistils (Fig 1j-1o) [31]. In fon1 and fon2 mutants, the lodicule number is altered, and homeotic conversion is limited to lodicules and stamens [29]. ...
... Apical dominance is enhanced by the production of plant hormones such as auxin, which inhibit the growth of axillary buds, thus reducing the tiller number [33]. Among all fon mutants identified to date, only the fon5 mutant exhibited the early flowering trait of fon7 (Table 1) [31]. ...
Floral organ number is crucial for successful seed setting and mature grain development. Although some genes and signaling pathways controlling floral organ number have been studied, the underlying mechanism is complicated and requires further investigation. In this study, a floral organ number mutant was generated by the ethyl methanesulfonate treatment of the Korean japonica rice cultivar Ilpum. In the floral organ number mutant, 37% of the spikelets showed an increase in the number of floral organs, especially stamens and pistils. Histological analysis revealed that the number of ovaries was determined by the number of stigmas; spikelets with two or three stigmas contained only one ovary, whereas spikelets with four stigmas possessed two ovaries. The floral organ number mutant showed pleiotropic phenotypes including multiple grains, early flowering, short plant height, and reduced tiller number compared with the wild-type. Genetic and MutMap analyses revealed that floral organ number is controlled by a single recessive gene located between the 8.0 and 20.0 Mb region on chromosome 8. Calculation of SNP-index confirmed Os08g0299000 as the candidate gene regulating floral organ number, which was designated as FLORAL ORGAN NUMBER7 ( FON7 ). A single nucleotide polymorphism (G to A) was discovered at the intron splicing donor site of FON7 , which caused the skipping of the entire sixth exon in the mutant, resulting in the deletion of 144 bp. Furthermore, the T-DNA-tagged line displayed the same floral organ number phenotype as the fon7 mutant. These results provide valuable insight into the mechanism of floral organ differentiation and formation in rice.
... DNA extraction and PCR were performed as described by Zhang et al. [33] and Zeng et al. [34], respectively. Briefly, a total of 179 polymorphic markers were used in QTL analysis. ...
Grain length is an important quantitative trait in rice (Oryza sativa L.) that influences both grain yield and exterior quality. Although many quantitative trait loci (QTLs) for grain length have been identified, it is still unclear how different alleles from different QTLs regulate grain length coordinately. To explore the mechanisms of QTL combination in the determination of grain length, five mapping populations, including two F2 populations, an F3 population, an F7 recombinant inbred line (RIL) population, and an F8 RIL population, were developed from the cross between the U.S. tropical japonica variety ‘Lemont’ and the Chinese indica variety ‘Yangdao 4’ and grown under different environmental conditions. Four QTLs (qGL-3-1, qGL-3-2, qGL-4, and qGL-7) for grain length were detected using both composite interval mapping and multiple interval mapping methods in the mapping populations. In each locus, there was an allele from one parent that increased grain length and another allele from another parent that decreased it. The eight alleles in the four QTLs were analyzed to determine whether these alleles act additively across loci, and lead to a linear relationship between the predicted breeding value of QTLs and phenotype. Linear regression analysis suggested that the combination of eight alleles determined grain length. Plants carrying more grain length-increasing alleles had longer grain length than those carrying more grain length-decreasing alleles. This trend was consistent in all five mapping populations and demonstrated the regulation of grain length by the four QTLs. Thus, these QTLs are ideal resources for modifying grain length in rice.
The three, by mutagenesis produced genes OsPi21, OsXa5, and OsBADH2, generated novel lines exhibiting desired fragrance and improved resistance.
Elite sterile lines are the basis for hybrid rice breeding, and rice quality and disease resistance become the focus of new sterile lines breeding. Since there are few sterile lines with fragrance and high resistance to blast and bacterial blight at the same time in hybrid rice production, we here integrated the simultaneous mutagenesis of three genes, OsPi21, OsXa5, and OsBADH2, into Zhi 5012S, an elite thermo-sensitive genic male sterile (TGMS) variety, using the CRISPR/Cas9 system, thus eventually generated novel sterile lines would exhibit desired popcorn-like fragrance and improved resistance to blast and bacterial blight but without a loss in major agricultural traits such as yield. Collectively, this study develops valuable germplasm resources for the development of two-line hybrid rice with disease resistance, which provides a way to rapid generation of novel TGMS lines with elite traits.
The number of grains per panicle is one of the most important factors of rice yield and determinated by branch and spikelet number. Genetic and molecular mechanisms responsible for panicle branching and spikelet development remain unclear in rice. Here, we report a mutant lax2-4 mainly showing lax panicle, longer grains, a little abnormal spikelet, lower setting rate and abaxial curled leaf. Genetic analysis indicated that the defective panicle phenotype of lax2-4 was controlled by single recessive gene. Further mapping and re-sequencing revealed that the fourth exon of LAX2 was lost caused by an approximately 2-Mb INV in lax2-4, thus LAX2-4 could be a new allele of LAX2. Overexpression assays showed that lax panicle was rescued in correspondence with the gradually increased expression level of wild-type LAX2-4 transcript. CRISPR/Cas9-mediated knockout of the fourth exon verified that LAX2-4 participates the regulation of sterile lemma and lemma development in rice. LAX2-4 could interact with an E-class gene, OsMADS1, and the fourth exon was necessary for its function. Collectively, we proposed that LAX2-4 plays a dual role in lateral spikelet and lemma development.
【Objective】The abnormal floral organ number mutant of rice was used to study the molecular mechanisms of floral organ development, and to identify the related genes of floral organ in rice. 【Method】In present study, a rice mutant, abnormal floral organ number1 (afon1) was isolated from an indica cultivar Zhenong 34 M2 population by mutagenesis with ethyl methane sulfonate (EMS). At flowering stage, five panicles from afon1 and Zhenong 34 were randomly selected to observe the morphological phenotype, cytological features and pollen fertility by histology analysis and scanning electron microscopy, respectively. At mature stage, ten plants from afon1 and Zhenong 34 were randomly chosen for measuring the main agronomic traits, such as plant height, number of tillering, panicle length, number of floret per panicle, number of filled grain per panicle and 1 000-grain weight. One hundred plump seeds were selected for calculating the germination potential and germination rate of the mutant afon1 and wild type. The F2 population from crossing of afon1 with WT Zhenong 34 and Zhenongda 104 were used for genetic analysis and gene mapping, respectively. Then, the DNA sequencing was conducted, the model of AFON1 protein was built and the space structure for AFON1 protein was analyzed. Moreover, the expression of candidate gene and floral organ number associated genes were detected by real-time PCR. 【Result】Compared with the wild type, the floral organ number of 59.64% spikelet was abnormal in mutant afon1, which most of them had a glume-like organ on the side of the leman and there were 2-4 rounds of floral organ number increased at the same time in others. Furthermore, the plant height and 1 000-grain weight of afon1 were visibly higher, while the seed setting rate was significantly reduced. The results of the genetic analysis showed that the phenotype of F1 population from the crossing of afon1
with Zhenong 34 was normal and the segregation ratio of wild-type and mutant phenotype plants from F2 population fitted a ratio of 3﹕1, which revealed that the mutant trait of afon1 was controlled by a single recessive nuclear gene. The afon1 was further mapped on the arm of chromosome 1 between InDel markers 1M5 and 1M18 with a physical distance of 73 kb, where there were 6 annotated genes. The sequencing results between the mutant afon1 and the wild type illustrated that there was a single base-pair substitution of
T (565th) to A on the exon of LOC_Os01g67430 resulting in the mutation of Trp (189th) to Arg. Protein sequencing and structure analysis revealed that there was a Lipase_3 domain and the mutation in the region changed the space structure of AFON1 obviously. The real-time PCR result showed that the expression of LOC_Os01g67430 in young panicle increased significantly, while the expression had no obvious difference in root, stem and leaf. Additionally, the expression of floral organ number related genes FON1 and FON2/4 was obviously increased in floral organ at young panicle developmental stage. 【Conclusion】The LOC_Os01g67430 was speculated as the gene afon1 regulating the number of floral organ by influencing the expression of corresponding genes which determined the number of floral organ.
Root hair is an important organ for uptaking nutrients and water in plant. A rice (Oryza sativa L.) mutant, ossrh3, with short root hairs was isolated from a T-DNA insertion mutant library of rice on Zhonghua 11 background. The elongation of root hairs in the mutant was severely impaired. Beside, some other traits were also affected, such as plant height, primary root length, lateral root length, and number of lateral roots. Genetic analysis indicated that the mutated phenotype was controlled by a single recessive nuclear gene. An F2 population was developed by crossing the mutant ossrh3 with an indica cultivar, Kasalath, to map the gene. Using simple sequence repeat (SSR) markers and newly designed sequence-tagged site (STS) markers, the target gene, OsSRH3, was located to a 37.7 kb region between markers S38978 and S39016 on chromosome 1. This marker interval contained 8 predicted genes.
A double mutant with streaked leaf and abnormal floret was found and temporarily named streaked leaf and floral organ number mutant (st-fon). For this mutant, besides white streak appeared on culm, leaves and panicles, the number of floral organs increased and florets cracked. The extreme phenotype was that several small florets grew from one floret or branch rachis in small florets extended and developed into panicles. By using transmission electron microscope to observe the ultrastructure of white histocytes of leaves at the seedling stage, the white tissues which showed abnormal plastids, lamellas and thylakoids could not develop into normal chloroplast, and the development of chloroplast was blocked at the early growth stage of plastid. Scanning electron microscope and paraffin section were also used to observe the development of floral organs, and the results indicated that the development of floral meristem was out of order and unlimited, whereas in the twisty leaves, vascular bundle sheath cells grew excessively, or some bubbly cells increased. Genetic analyses carried out by means of cross and backcross with four normal-leaf-color materials revealed that the mutant is of cytoplasm inheritance.
A rice lesion mimic mutant, lm3, was obtained by the mutagenesis of an indica cultivar, 93-11, using γ-ray radiation. Brownish lesions appeared on the leaves of lm3 at the young seedling stage and persisted until the ripening stage. The lm3 mutant was characterised by a shorter plant height and delayed heading compared with the wild-type 93-11. A genetic analysis indicated that the lesion mimic phenotype was controlled by a single recessive gene. Using simple sequence repeat (SSR) markers, the target gene LM3 was first located between marker RM5748 and RM14906 on chromosome 3. We then developed Insertion-Deletion (InDel) markers to fine-map LM3, and the locus was localised to a 29 kb region defined by two InDel markers, In12571 and In12600. Five ORFs were predicted in the candidate region, and DNA sequencing detected a single-nucleotide polymorphism (SNP) in the coding region of LOC Os03g21900. The SNP in the fourth exon (C in 93-11; T in lm3) of LOC_Os03g21900 results in the substitution of a proline (P) with a serine (S) at the 140th amino acid of the deduced uroporphyrinogen decarboxylase protein. We did not detect polymorphisms in the other predicted ORF regions between lm3 and 93-11. These results suggest that LOC_Os03g21900 is the most likely candidate gene for LM3.
A short root mutant ksr1 with the Kasalath background was isolated from an EMS-mutagenized population in rice. The root length of 6-day-old ksr1 seedlings was only about 20% of the wild type. Genetic analysis indicated that the short root phenotype of ksr1 was controlled by a recessive mutation in a single nuclear-encoded gene. To map the ksr1 mutation, an F2 population was generated by crossing the ksr1 mutant with Nipponbare. The KSR1 locus was linked to the SSR marker RM1223 on rice chromosome 4. Eight new SSR markers and two InDel markers were developed around this marker. KSR1 gene was further mapped to a 155 kb region, flanked by the InDel marker 4-24725K and the SSR marker RM17182.
