Summary
Rice grain filling rate contributes largely to grain productivity and accumulation of nutrients. MicroRNAs (miRNAs) are key regulators of development and physiology in plants and become a ...novel key target for engineering grain size and crop yield. However, there is little studies, so far, showing the miRNA regulation of grain filling and rice yield, in consequence. Here, we show that suppressed expression of rice miR1432 (STTM1432) significantly improves grain weight by enhancing grain filling rate and leads to an increase in overall grain yield up to 17.14% in a field trial. Molecular analysis identified rice Acyl‐CoA thioesterase (OsACOT), which is conserved with ACOT13 in other species, as a major target of miR1432 by cleavage. Moreover, overexpression of miR1432‐resistant form of OsACOT (OXmACOT) resembled the STTM1432 plants, that is, a large margin of an increase in grain weight up to 46.69% through improving the grain filling rate. Further study indicated that OsACOT was involved in biosynthesis of medium‐chain fatty acids. In addition, RNA‐seq based transcriptomic analyses of transgenic plants with altered expression of miR1432 demonstrated that downstream genes of miR1432‐regulated network are involved in fatty acid metabolism and phytohormones biosynthesis and also overlap with the enrichment analysis of co‐expressed genes of OsACOT, which is consistent with the increased levels of auxin and abscisic acid in STTM1432 and OXmACOT plants. Overall, miR1432‐OsACOT module plays an important role in grain filling in rice, illustrating its capacity for engineering yield improvement in crops.
Leaf angle is a key factor in plant architecture and crop yield. Brassinosteroids (BRs) regulate many developmental processes, especially the leaf angle in monocots. However, the BR signalling ...pathway is complex and includes many unknown members. Here, we propose that
Oryza sativa BRASSINOSTEROID-RESPONSIVE LEAF ANGLE REGULATOR 1
(
OsBLR1
) encodes a bHLH transcription factor, and positively regulates BR signalling to increase the leaf angle and grain length in rice (
Oryza sativa
L.). Lines overexpressing
OsBLR1
(
blr1-D
and
BLR1-OE-1/2/3
) had similar traits, with increased leaf angle and grain length. Conversely,
OsBLR1
-knockout mutants (
blr1-1/2/3
) had erect leaves and shorter grains. Lamina joint inclination, coleoptile elongation, and root elongation assay results indicated that these overexpression lines were more sensitive to BR, while the knockout mutants were less sensitive. There was no significant difference in the endogenous BR contents of
blr1-1/2
and wild-type plants. These results suggest that OsBLR1 is involved in BR signal transduction. The
blr1-D
mutant, with increased cell growth in the lamina joint and smaller leaf midrib, showed significant changes in gene expression related to the cell wall and leaf development compared with wild-type plants; furthermore, the cellulose and protopectin contents in
blr1-D
were reduced, which resulted in the increased leaf angle and bent leaves. As the potential downstream target gene of OsBLR1, the
REGULATOR OF LEAF INCLINATION1
(
OsRLI1
) gene expression was up-regulated in
OsBLR1
-overexpression lines and down-regulated in
OsBLR1
-knockout mutants. Moreover, we screened OsRACK1A as an interaction protein of OsBLR1 using a yeast two-hybrid assay and glutathione-S-transferase pull-down.
Key message
The overexpression of
OsBLR1
caused increased leaf angle and grain length, whereas
OsBLR1
-knockout mutants had the opposite phenotypes. OsBLR1 is a member in BR signalling pathway.
Nitrogen is one of the important factors for high yield of rice. Apart from high yield, high quality has become the current urgent demand for rice production. Grain-filling stage is crucial for rice ...yield and quality formation. However, the effect of nitrogen on grain-filling characteristics and the relationship of grain-filling characteristics and rice quality of mid-season indica rice were still unclear. A field experiment was carried out to ascertain the critical grain-filling characteristics that contribute to rice milling quality, appearance quality and cooking and eating quality under nitrogen applications. The results showed that nitrogen applications prolonged the duration of superior and inferior grain filling. The mean grain-filling rate (Gmean) and the maximum grain-filling rate (Gmax) of the inferior grains were positively correlated with chalky kernel rate, chalkiness, and amylose content. The time reaching the maximum grain-filling rate (Tmax G) of the inferior grains was positively correlated with brown rice rate, milled rice rate, and head milled rice rate. Chalky kernel rate and chalkiness were negatively correlated with peak paste viscosity and breakdown viscosity. Less amylose content and more crude protein content were detected in nitrogen application of Liangyoupei 9 and Y Liangyou 2 both in 2016 and 2017. According to the correlation analysis, better cooking and eating quality of Y Liangyou 2 which had less amylose content might result from its higher Gmax and Gmean of inferior grain than that of Liangyoupei 9 in the treatments of nitrogen application. These results indicated that the prolonging grain-filling duration and increasing grain weight at the maximum grain-filling rate of inferior grains contributed to the improvement of milling quality, appearance quality, and cooking and eating quality of mid-season indica rice under appropriate nitrogen applications.
As representative varieties of the four phases of the super rice breeding project in China, Lianyoupei 9 (LYP9), Y Liangyou 1 (YLY1), Y Liangyou 2 (YLY2), and Y Liangyou 900 (YLY900) achieved higher ...yield under optimal cultivation techniques. However, the impact of these high-yield rice varieties on greenhouse gas (GHG) emissions under high-yield cultivation management practices remains poorly understood. In this study, we conducted field experiments to investigate CH
4
and N
2
O emissions from paddies containing four elite rice varieties, managed with field drying at the ineffective tillering stage and alternate wet/dry irrigation at the grain-filling stage. The plants were fertilised with nitrogen (N) at three different rates. The results showed that CH
4
emission was highest at the tillering stage. N
2
O emission flux was dramatically increased by field drying at the ineffective tillering stage, and with the rate of N application. Rice variety was among the most important factors affecting CH
4
emission and global warming potential (GWP). N
2
O emission was mainly related to N application rate rather than rice variety. YLY2 achieved higher yield than LYP9, YLY1, and YLY900, and lower GHG emission than YLY900. Our results indicate that rice variety should be considered as a key factor to reduce GHG emissions from rice paddies under high-yield cultivation practices. Based on its high yield and low GHG emission at the study site, YLY2 may be an optimal rice variety.
We carried out a pool culture experiment to determine the optimal water treatment depth in loam and clay soils during the late growth stage of super rice. Three controlled water depth treatments of ...0-5, 0-10 and 0-15 cm below the soil surface were established using alternate wetting and drying irrigation, and the soil water potential （0 to -25 kPa） was measured at 5, 10 and 15 cm. A 2-cm water layer was used as the control. We measured soil enzyme activities, root antioxidant enzyme activities, chlorophyll fluorescence parameters, and rice yield. The results showed that the 0-5-cm water depth treatment significantly increased root antioxidant enzyme activities in loam soil compared with the control, whereas soil enzyme activities, chlorophyll fluorescence parameters and yield did not differ from those of the control. The 0-10- and 0-15-cm water depth treatments also increased root antioxidant enzyme activities, whereas soil enzyme activities, chlorophyll fluorescence parameters and yield decreased. In clay soil, the soil enzyme activities, root antioxidant enzyme activities, chlorophyll fluorescence parameters, and yield did not change with the 0-5-cm water treatment, whereas the 0-10- and 0-15-cm water treatments improved these parameters. Therefore,the appropriate depths for soil water during the late growth period of rice with a 0 to -25 kPa water potential were 5 cm in loam and 15 cm in clay soil.
High molecular weight glutenin subunits (HMW-GSs), encoded by the genes at Glu-1 loci in wheat and its related species, are significant in the determination of grain processing quality. However, the ...diversity and variations of HMW-GSs are relatively low in bread wheat. More interests are now focused on wheat wild relatives in Triticeae. The genus Aegilops represents an important germplasm for novel HWM-GSs and other useful genes for wheat genetic improvement.
Six novel Glu-1 alleles and HMW-GSs were identified and characterized from three species of Aegilops section Sitopsis (S genome). Both open reading frames (ORFs) and promoter regions of these Glu-1 alleles were sequenced and characterized. The ORFs of Sitopsis Glu-1 genes are approximately 2.9 kb and 2.3 kb for x-type and y-type subunits, respectively. Although the primary structures of Sitopsis HMW-GSs are similar to those of previously reported ones, all six x-type or y-type subunits have the large fragment insertions. Our comparative analyses of the deduced amino acid sequences verified that Aegilops section Sitopsis species encode novel HMW-GSs with their molecular weights larger than almost all other known HMW-GSs. The Glu-1 promoter sequences share the high homology among S genome. Our phylogenetic analyses by both network and NJ tree indicated that there is a close phylogenetic evolutionary relationship of x-type and y-type subunit between S and D genome.
The large molecular weight of HMW-GSs from S genome is a unique feature identified in this study. Such large subunits are resulted from the duplications of repetitive domains in Sitopsis HMW-GSs. The unequal crossover events are the most likely mechanism of variations in glutenin subunits. The S genome-encoded subunits, 1Dx2.2 and 1Dx2.2* have independent origins, although they share similar evolutionary mechanism. As HMW-GSs play a key role in wheat baking quality, these large Sitopsis glutenin subunits can be used as special genetic resources for wheat quality improvement.
Superior grains determined by grain weight are not fully correlated with the flowering order in rice PENG Ting, L Qiang, ZHAO Ya-fan, SUN Hong-zheng, HAN Ying-chun, DU Yan-xiu, ZHANG Jing, LI Jun-zhou, WANG Lin-lin, ZHAO Quan-zhi (State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, P.R.China)
Journal of Integrative Agriculture,
05/2015, Letnik:
14, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Rice panicles are composed of many branches with two types of extreme grains,the superior and the inferior.Traditionally,it has been well accepted that earlier flowers result in superior grains and ...late flowers generate inferior grains.However,these correlations have never been strictly examined in practice.In order to determine the accurate relationship between superior and inferior grains and the flowering order,we localized all the seeds in a panicle in four distinct rice species and systematically documented the rice flowering order,flower locations and the final grain weight for their relationships.Our results demonstrated that the grain weight is more heavily determined by the position of the seeds than by the flowering order.Despite earlier flowering has a positive correlation with the grain weight in general,grains from flowers blooming on the second day after anthesis generally gained the highest weight.This suggests earlier flowers may not result in superior grains.Therefore,we concluded that superior and inferior grains,commonly determined by grain weight,are not fully correlated with the flowering order in rice.Following the order of the grain weight,the superior grains are generally localized at the middle parts of the primary branches,whereas inferior grains were mainly on the last two secondary branches of the lower half part of the panicle.In addition,the weight of inferior grains were affected by spikelet thinning and spraying with exogenous plant growth regulators,indicating that physiological incompetence might be the major reason for the occurrence of the inferior grains.
The influence of sulphur on the accumulation and metabolism of arsenic in rice was investigated. Rice seedlings were grown in nutrient solutions with low sulphate (1.8
μM SO
4
2−) or high sulphate ...(0.7
mM SO
4
2−) for 12 or 14
d, before being exposed to 10
μM arsenite or arsenate for 2 or 1
d, respectively. In the arsenite exposure treatment, low sulphate-pretreated rice accumulated less arsenite than high sulphate pretreated plants, but the arsenite concentrations in shoots of low sulphate pretreated rice were higher than those of high sulphate pretreated. In the arsenate exposure treatment, the low sulphate pre-treatments also resulted in less arsenite accumulation in rice roots. Sulphur deprivation in nutrient solution decreased the concentrations of non-protein thiols in rice roots exposed to either arsenite or arsenate. The low sulphate-pretreated plants had a higher arsenic transfer factor than the high sulphate-pretreated plants. The results suggest that rice sulphate nutrition plays an important role in regulating arsenic translocation from roots to shoots, possibly through the complexation of arsenite-phytochelatins.
Test of Small RNA Sequencing Repeatability in Rice SUN Hong-zheng PENG Ting ZHANG Jing LI Jun-zhou DU Yan-xiu ZHAO Quan-zhi
Rice science,
2017, January 2017, 2017-01-00, 2017-01-01, Letnik:
24, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Deep sequencing of small RNAs（sR NA） is widely used in sR NAs studies in plants. In order to investigate the sequencing frequency variation of sR NAs, the same sR NA samples from rice grains were ...sequenced twice using deep sequencing technique. The sR NAs were classified into three categories, high abundance（〉 100 RPM）, medium abundance（10–100 RPM） and low abundance（1–10 RPM）. According to the repeat sequencing data of the same sample, highly expressed sR NAs（〉 100 RPM） were less subject to random drift, and 95% of the sR NAs Log2 ratio between two samples fell between-0.649 and 0.558. The same trend was observed in mediumly expressed sR NAs（10–100 RPM）, and 95% of the Log2 ratio fell between-0.535 and 0.759. As to lowly expressed sR NAs（1–10 RPM）, 95% of the Log2 ratio varied between-1.009 and 1.011. These results can be used as a theoretical guide to find differentially expressed s RNAs in sR NA studies in plants.
Wide crossing is a useful method for transferring traits of interest from wild Triticeae species to wheat. In this study, Aegilops sharonensis was successfully hybridized to three tetraploid wheat ...species with crossability varying from 0.86 to 1.76 %. F1 hybrids were verified by their display of intermediate characteristics in morphology, cytology, and sodium dodecyl sulfate–polyacrylamide gel electrophoresis profiles. The exogenous x- and y-type subunits of high-molecular-weight glutenin subunits of Ae. sharonensis were expressed in F1 hybrid seeds and showed identical electrophoretic mobilities to those originally present in Ae. sharonensis. In F2 hybrids, the x-type subunit migrated faster, indicating that a decrease in molecular mass had occurred. Cloning of the open reading frames of subunit variants revealed that the x-type subunit had protein sequence variations, including single residue mutations, and insertions and deletions involving one or more repeat motifs. The two deletions causing the size reduction of the exogenous x-subunits of Ae. sharonensis in the F2 seeds were most likely the result of slip-mismatching.
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