Main conclusion
We have developed long term stable high yielding rice lines, Hybrid Mimics, from commercial hybrids. The vigour of the Mimic and the hybrid are developmental changes. These Mimics ...could substitute for hybrid seed for planting.
We have used two pre-existing high-yielding hybrid systems (
FLY1
and
DY527
) to develop Hybrid Mimics. In the
FLY1
hybrid system we selected, under field conditions, F6 lines which have high grain yields and biomass equivalent to the F1 hybrids, stable over subsequent F7, F8 and later generations. We have termed these lines Hybrid Mimics. The mimics are mostly homozygous as a consequence of selfing in each generation. We have repeated this selection procedure in the second independent hybrid system
DY527,
producing Mimics with similar characteristics to the F1 hybrid. In both hybrid systems the selection criterion, based on the phenotype of the F1 hybrid, results in the Mimics having grain yield and biomass similar to that of the F1 hybrid. In each generation of the breeding program the plant population has increased phenotypic homogeneity. The genomes of the Mimic plants do not contain any common heterozygous segments negating claims that the vigour of hybrids depends upon heterozygosity of particular loci. Both hybrids and Mimics have early germination and commence photosynthesis before the parents, providing enhanced growth which is maintained throughout the life cycle. The biochemical parameters of photosynthesis in the hybrids and Mimics do not differ from those of the parents. Grain quality and resistance to the two major diseases, bacterial blight and rice blast are similar in the Mimics and hybrids. The Mimics overcome the major disadvantage of hybrids where F2 phenotypic segregation prevents their use as a crop beyond the F1 generation.
Summary
Herein, a novel series of dual histone deacetylase (HDAC) and vascular endothelial growth factor receptor (VEGFR) inhibitors were designed, synthesized and biologically evaluated based on ...previously reported pazopanib-based HDAC and VEGFR dual inhibitors. Most target compounds showed significant HDAC1, HDAC6 and VEGFR2 inhibition, which contributed to their potent antiproliferative activities against multiple cancer cell lines and significant antiangiogenic potencies in both human umbilical vein endothelial cell (HUVEC) tube formation assays and rat thoracic aorta ring assays. Further HDAC selectivity evaluations indicated that hydroxamic acids
5
and
9e
possessed HDAC isoform selectivity profiles similar to that of the approved HDAC inhibitor suberoylanilide hydroxamic acid(SAHA), while hydrazide
12
presented an HDAC isoform selectivity profilesimilar to that of the clinical HDAC inhibitor MS-275. The VEGFR inhibition profiles of
5, 9e
and
12
were similar to that of the approved VEGFR inhibitor pazopanib. The intracellular target engagements of Compounds
5
and
12
were confirmed by western blot analysis. The metabolic stabilities of
5, 9e
and
12
in mouse liver microsomes were inferior to that of pazopanib. These dual HDAC and VEGFR inhibitors provide lead compounds for further structural optimization to obtainpolypharmacological anticancer agents.
Black and red rice are rich in both anthocyanin and proanthocyanin content, which belong to a large class of flavonoids derived from a group of phenolic secondary metabolites. However, the molecular ...pathways and mechanisms underlying the flavonoid biosynthetic pathway are far from clear. Therefore, this study was undertaken to gain insight into physiological factors that are involved in the flavonoid biosynthetic pathway in rice cultivars with red, black, and white colors. RNA sequencing of caryopsis and isobaric tags for relative and absolute quantification (iTRAQ) analyses have generated a nearly complete catalog of mRNA and expressed proteins in different colored rice cultivars. A total of 31,700 genes were identified, of which 3417, 329, and 227 genes were found specific for red, white, and black rice, respectively. A total of 13,996 unique peptides corresponding to 3916 proteins were detected in the proteomes of black, white, and red rice. Coexpression network analyses of differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) among the different rice cultivars showed significant differences in photosynthesis and flavonoid biosynthesis pathways. Based on a differential enrichment analysis, 32 genes involved in the flavonoid biosynthesis pathway were detected, out of which only
,
,
, and
were detected by iTRAQ. Taken together, the results point to differences in flavonoid biosynthesis pathways among different colored rice cultivars, which may reflect differences in physiological functions. The differences in contents and types of flavonoids among the different colored rice cultivars are related to changes in base sequences of Os06G0162500, Os09G0455500, Os09G0455500, and Os10G0536400. Current findings expand and deepen our understanding of flavonoid biosynthesis and concurrently provides potential candidate genes for improving the nutritional qualities of rice.
Molecular-assisted breeding is an effective way to improve targeted agronomic traits.
(
) is a pleiotropic gene that regulates yield, quality, disease resistance, and stress tolerance, traits that ...are of great value in rice (
L.) breeding. In this study, a colorimetric LAMP (loop-mediated isothermal amplification) assay was developed for the detection of the
allele and tested for the screening and selection of the heavy-panicle hybrid rice elite restorer line SHUHUI498, modified with the allele. InDel (Insertion and Deletion) primers (DEP1_F and DEP1_R) and LAMP primers (F3, B3, FIP, and BIP) for genotyping were designed using the Primer3 Plus (version 3.3.0) and PrimerExplore (version 5) software. Our results showed that both InDel and LAMP markers could be used for accurate genotyping. After incubation at a constant temperature of 65 °C for 60 min with hydroxynaphthol blue (HNB) as a color indicator, the color of the LAMP assay containing the
allele changed to sky blue. The SHUHUI498 rice line that was detected in our LAMP assay displayed phenotypes consistent with the
allele such as having a more compact plant architecture, straight stems and leaves, and a significant increase in the number of effective panicles and spikelets, demonstrating the effectiveness of our method in screening for the
allele in rice breeding.
Catalases (CATs) are important self-originating enzymes and are involved in many of the biological functions of plants. Multiple forms of CATs suggest their versatile role in lesion mimic mutants ...(LMMs), H2O2 homeostasis and abiotic and biotic stress tolerance. In the current study, we identified a large lesion mimic mutant9428 (llm9428) from Ethyl-methane-sulfonate (EMS) mutagenized population. The llm9428 showed a typical phenotype of LMMs including decreased agronomic yield traits. The histochemical assays showed decreased cell viability and increased reactive oxygen species (ROS) in the leaves of llm9428 compared to its wild type (WT). The llm9428 showed enhanced blast disease resistance and increased relative expression of pathogenesis-related (PR) genes. Studies of the sub-cellular structure of the leaf and quantification of starch contents revealed a significant decrease in starch granule formation in llm9428. Genetic analysis revealed a single nucleotide change (C > T) that altered an amino acid (Ala > Val) in the candidate gene (Os03g0131200) encoding a CATALASE C in llm9428. CRISPR-Cas9 targetted knockout lines of LLM9428/OsCATC showed the phenotype of LMMs and reduced starch metabolism. Taken together, the current study results revealed a novel role of OsCATC in starch metabolism in addition to validating previously studied functions of CATs.
Panicle degeneration, sometimes known as abortion, causes heavy losses in grain yield. However, the mechanism of naturally occurring panicle abortion is still elusive. In a previous study, we ...characterized a mutant, apical panicle abortion1331 (apa1331), exhibiting abortion in apical spikelets starting from the 6 cm stage of panicle development. In this study, we have quantified the five phytohormones, gibberellins (GA), auxins (IAA), abscisic acid (ABA), cytokinins (CTK), and brassinosteroids (BR), in the lower, middle, and upper parts of apa1331 and compared these with those exhibited in its wild type (WT). In apa331, the lower and middle parts of the panicle showed contrasting concentrations of all studied phytohormones, but highly significant changes in IAA and ABA, compared to the upper part of the panicle. A comparative transcriptome of apa1331 and WT apical spikelets was performed to explore genes causing the physiological basis of spikelet abortion. The differential expression analysis revealed a significant downregulation and upregulation of 1587 and 978 genes, respectively. Hierarchical clustering of differentially expressed genes (DEGs) revealed the correlation of gene ontology (GO) terms associated with antioxidant activity, peroxidase activity, and oxidoreductase activity. KEGG pathway analysis using parametric gene set enrichment analysis (PGSEA) revealed the downregulation of the biological processes, including cell wall polysaccharides and fatty acids derivatives, in apa1331 compared to its WT. Based on fold change (FC) value and high variation in expression during late inflorescence, early inflorescence, and antherdevelopment, we predicted a list of novel genes, which presumably can be the potential targets of inflorescence development. Our study not only provides novel insights into the role of the physiological dynamics involved in panicle abortion, but also highlights the potential targets involved in reproductive development.
Vacuolar invertase is involved in sugar metabolism and plays a crucial role in plant growth and development, thus regulating seed size. However, information linking vacuolar invertase and seed size ...in rice is limited. Here we characterized a small grain mutant
(grain size on chromosome 2) that showed a reduced in grain size and 1000-grain weight compared to the wild type. Map-based cloning and genetic complementation showed that
is responsible for the observed phenotype. Loss-of-function of
resulted in grains of smaller size when compared to the wild type, while overexpression showed increased grain size. We also obtained a T-DNA insertion mutant of
, which is a homolog of
and generated double knockout (
) mutants of
and
using CRISPR/Cas9. Genetic data showed that
, that has no effect on grain size by itself, reduces grain length and width in the absence of
. Altered sugar content with increased sucrose and decreased hexose levels, as well as changes vacuolar invertase activities and starch constitution in
,
,
mutants indicate that
and
affect sucrose metabolism in sink organs. In summary, we identified
as a positive regulator of grain size in rice, and while
has no function on grain size by itself. In the absence of
, it is possible to detect a role of
in the regulation of grain size. Both
and
are involved in sucrose metabolism, and thus regulate grain size. Our findings increase our understanding of the role of
and its homolog,
, in grain size development and also suggest a potential strategy to improve grain yield in rice.
Lesion mimic mutants display spontaneous cell death, and thus are valuable for understanding the molecular mechanism of cell death and disease resistance. Although a lot of such mutants have been ...characterized in rice, the relationship between lesion formation and abscisic acid (ABA) synthesis pathway is not reported. In the present study, we identified a rice mutant,
(
), exhibiting spontaneous cell death, pre-harvest sprouting, enhanced growth, and resistance to rice bacterial and blast diseases. Cell death in the mutant was accompanied with excessive accumulation of H
O
. Enhanced disease resistance was associated with cell death and upregulation of defense-related genes. Map-based cloning identified a G-to-A point mutation resulting in a D-to-N substitution at the amino acid position 110 of OsABA2 (LOC_Os03g59610) in
. Knock-out of
through CRISPR/Cas9 led to phenotypes similar to those of
. Consistent with the function of
in ABA biosynthesis, ABA level in the
mutant was significantly reduced. Moreover, exogenous application of ABA could rescue all the mutant phenotypes of
. Taken together, our data linked ABA deficiency to cell death and provided insight into the role of ABA in rice disease resistance.
Panicle is a harvesting organ of rice, and its morphology and development are closely associated with grain yield. The current study was carried on a mutant screened through an EMS (ethyl-methane ...sulphonate) mutagenized population of a Japonica cultivar Kitaake (WT). A mutant, named as asp-lsl (aberrant spikelet-long sterile lemma), showed a significant decrease in plant height, number of tillers, thousand-grains weight, seed setting rate, spikelet length, kernel length and effective number of grains per panicle as compared to WT. Asp-lsl showed a pleiotropic phenotype coupled with the obvious presence of a long sterile lemma. Cross-sections of lemma showed an increase in the cell volume rather than the number of cells. Genetic segregation analysis revealed its phenotypic trait is controlled by a single recessive nuclear gene. Primary and fine mapping indicated that candidate gene controlling the phenotype of asp-lsl was located in an interval of 212 kb on the short arm of chromosome 8 between RM22445 and RM22453. Further sequencing and indels markers analysis revealed LOC_Os08g06480 harbors a single base substitution (Gright arrowA), resulting in a change of 521st amino acid(Glyright arrowGlu. The homology comparison and phylogenetic tree analysis revealed mutation was occurred in a highly conserved domain and had a high degree of similarity in Arabidopsis, corn, and sorghum. The CRISPR/Cas9 mutant line of ASP-LSL produced a similar phenotype as that of asp-lsl. Subcellular localization of ASP-LSL revealed that its protein is localized in the nucleus. Relative expression analysis revealed ASP-LSL was preferentially expressed in panicle, stem, and leaves. The endogenous contents of GA, CTK, and IAA were found significantly decreased in asp-lsl as compared to WT. Current study presents the novel phenotype of asp-lsl and also validate the previously reported function of OsREL2 (ROMOSA ENHANCER LOCI2), / ASP1(ABERRANT SPIKELET AND PANICLE 1).
Salicylic acid (SA) is a stress hormone synthesized in phenylalanine ammonia-lyase (PAL) and the branching acid pathway. SA has two interconvertible forms in plants: SAG (SA O-β-glucoside) and SA ...(free form). The molecular mechanism of conversion of SA to SAG had been reported previously. However, which genes regulate SAG to SA remained unknown. Here, we report a cytoplasmic β-glucosidase (β-Glu) which participates in the SA pathway and is involved in the brown hull pigmentation in rice grain. In the current study, an EMS-generated mutant brown hull 1 (bh1) displayed decreased contents of SA in hulls, a lower photosynthesis rate, and high-temperature sensitivity compared to the wild type (WT). A plaque-like phenotype (brown pigmentation) was present on the hulls of bh1, which causes a significant decrease in the seed setting rate. Genetic analysis revealed a mutation in LOC_Os01g67220, which encodes a cytoplasmic Os1βGlu4. The knock-out lines displayed the phenotype of brown pigmentation on hulls and decreased seed setting rate comparable with bh1. Overexpression and complementation lines of Os1βGlu4 restored the phenotype of hulls and normal seed setting rate comparable with WT. Subcellular localization revealed that the protein of Os1βGlu4 was localized in the cytoplasm. In contrast to WT, bh1 could not hydrolyze SAG into SA in vivo. Together, our results revealed the novel role of Os1βGlu4 in the accumulation of flavonoids in hulls by regulating the level of free SA in the cellular pool.
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