Auxin-brassinosteroid crosstalk:Regulating rice plant architecture and grain shape

Rice(Oryza sativa)plant architecture and grain shape,which determine grain quality and yield,are modulatedby auxin and brassinosteroid via regulation of cell elongation and proliferation.We review the signaltransduction of these hormones and the crosstalk between their signals on the regulation of rice plantarchitecture and grain shape.

Grain Shape Genes:Shaping the Future of Rice Breeding

The main goals of rice breeding nowadays include increasing yield,improving grain quality,and promoting complete mechanized production to save labor costs.Rice grain shape,specified by three dimensions,including grain length,width and thickness,has a more precise meaning than grain size,contributing to grain appearance quality as well as grain weight and thus yield.Furthermore,the divergence of grain shape characters could be utilized in mechanical seed sorting in hybrid rice breeding systems,which has been succeeded in utilizing heterosis to achieve substantial increase in rice yield in the past decades.Several signaling pathways that regulate rice grain shape have been elucidated,including G protein signaling,ubiquitination-related pathway,mitogen-activated protein kinase signaling,phytohormone biosynthesis and signaling,micro RNA process,and some other transcriptional regulatory pathways and regulators.This review summarized the recent progress on molecular mechanisms underlying rice grain shape determination and the potential of major genes in future breeding applications.

Progress of Genetic Research on Grain Shape in Rice

Grain character is an important factor in yield components of rice. Progress of genetic research on grain length, grain width, lengthwidth ratio, grain thickness and grain weight were reviewed. It＇s considered that the genetic research on grain shape in rice has achieved considerable progress by exploration on genetic research for many years, but there are still some aspects waiting to be strengthened such as the grain shape, the genetic mechanism of grain shape and the genetic and potential value of grain shape in characteristic germplasm resources, etc.

QTL Detection for Rice Grain Shape Using Chromosome Single Segment Substitution Lines

Rice grain shape is one of the important factors affecting grain quality and yield,but it is liable to be influenced by genetic backgrounds and environments.The chromosome single segment substitution lines(SSSLs) in rice have been considered as ideal populations to identify the quantitative trait loci(QTLs).In this study,22 QTLs affecting rice grain shape were detected to be distributed on eight chromosomes except chromosomes 6,9,11 and 12 by using SSSLs.Among them,seven QTLs conditioned grain length,six conditioned grain width,five affected grain length-width ratio and four controlled grain thickness.

GRAIN SHAPE EFFECT IN SUPERPLASTIC DEFORMATION

The method controlling grain shape in TMT processing and the effect of grain shape on char- acteristic parameters in superplastic deformation were discussed.The accommodation velocity of grahl boundary sliding,which is the dominant mechanism in superplastic deformation,and the contribution of each mechanism to the total strain,as influenced by grain shape,were ana- lyzed.Grain shape has been shown to be an essential structural factor for superplasticity.Then an analysis was made about the effect of grain shape on the region transition strain rate so that a new concept,critical aspect for superplasticity,was worked out.These predictions were compared with the measured results in an Al-Zn-Mg alloy.

INFLUENCE OF GRAIN SHAPE AND CARBIDE ON CREEP CRACK GROWTH IN HK40

The influence of two different grain shapes and carbides in the HK40 alloy,the material for use of furnace tube,on the rate of creep crack growth has been investigated.The resistance to creep crack growth of the material with columnar grains is inferior than that with equiaxial grains when the load line is perpendicular to the columnar grain axis.The influence of secon- dary carbide on the rate of creep crack propagation depends upon the Brain shape.

Effects of Initial Static Shear Stress and Grain Shape on Liquefaction of Saturated Nanjing Sand

This paper mainly investigates the effects of initial static shear stress and grain shape on the liquefaction induced large deformation of saturated sand under torsional shear.Nanjing sand,mainly composed of platy grains,is tested with different initial static shear stress ratio(SSR)using a hollow column torsional shear apparatus.The tests find that the saturated Nanjing sand reaches full liquefaction under the superposition of initial static shear stress and cyclic stress for both stress reversal and non-reversal cases.However,it requires a large number of loading cycles to reach full liquefaction if stress reversal does not occur.With increasing the initial static stress,the large deformation of the Nanjing sand should mainly induced by the cyclic liquefaction firstly under a smaller initial shear stress,and then it should be induced by the residual deformation failure.The critical point occurs approximately when the initial shear stress is close to the amplitude of the cyclic shear stress.Meanwhile,it shows that grain angularity increases the liquefaction resistance when the initial static shear stress is zero.A small initial static shear stress causes the larger loss of liquefaction resistance for angular sand than rounded sand.At a high initial SSR,the angular sand is more resistant to the large residual deformation failure than the rounded sand.

Source to sink zircon grain shape:Constraints on selective preservation and significance for Western Australian Proterozoic basin provenance

The effect of selective preservation during transportation of zircon grains on the detrital age spectrum is difficult to quantify and could potentially lead to systematic bias in provenance analysis. Here we investigate whether the shape of detrital zircon grains holds provenance information and if the grain shape can assist in understanding preservation. We applied multiple linear regression analysis to identify significant shape properties in detrital zircons from Proterozoic metasediments of the Capricorn and Amadeus basins and their Archean and Proterozoic sources in the Yilgarn Craton and the Musgrave Province in Western Australia. Digital images and isotopic data from 819 SIMS U-Pb dated zircons were examined for correlation between grain shape, age, U and Th content. Out of twelve shape descriptors measured, Minor Axis, the width of zircon grains perpendicular to the crystallographic c-axis, consistently shows the most significant correlation with isotopic age. In the studied population Archean grains are narrower than Proterozoic grains: the probability that grains wider than 75 μm are Archean is less than30%.Calculations of the proportions of source material in sedimentary rocks relative to the proportions of source material in the overall catchment area(erosion parameter 'K' calculated based on age spectra)produced values typical for mature river systems, with K = 6 for the Yilgarn-Capricorn and K = 5.5 for the Musgrave-Amadeus source-sink system. For the Yilgarn-Capricorn system, we also calculated 'K' based on Minor Axis, to determine whether grain width can be linked to age populations. Results of the shapebased K of 5.3 suggest a similarity between age-based and shape-based 'K' values, demonstrating that zircon grain width may be a useful discriminator of provenance. Contrary to commonly applied qualitative shape classifications, we found no consistent correlations between shape descriptors of magmatic zircons and the composition of their host rock. While metamict zircons were preferentially removed during transport, the similarities in grain shape and age distribution of magmatic and detrital populations suggest that hydraulic sorting did not have a significant effect. We conclude that transport of zircon grains from magmatic source to sedimentary sink affects their width less than their length.

Genome-Wide Association Analysis and Allelic Mining of Grain Shape-Related Traits in Rice

Excavating single nucleotide polymorphisms (SNPs) significantly associated with rice grain shape and predicting candidate genes through genome-wide association study (GWAS) can provide a theoretical basis for discovery and utilization of excellent genetic resources in rice. Based on 16 352 SNPs, 161 natural indica rice varieties with various grain sizes in southern China were used for GWAS of grain shape-related traits, referring to grain length (GL), grain width (GW), 1000-grain weight (TGW), and grain length/width (GLW). Phenotypic statistics showed that coefficient of variation values for these four traits GL, GW, TGW and GLW were 9.92%, 9.09%, 20.20% and 16.38%, respectively. Each trait showed a normal distribution, and there was a certain correlation between these traits. Through general linear model correlation analysis, a total of 38 significant loci were identified, and a range of 100 kb upstream and downstream of the significant loci was identified as the candidate interval. On chromosome 3, GS3 and qGL3 were found to regulate GL. On chromosome 6, TGW6 and GW6a were found to regulate TGW. Also, some QTLs related to grain shape were found on chromosomes 5 and 9. Besides that, using sequenced 3K-germplasm resources, we found that there are 22 overlapped varieties between these two natural populations. Twenty-six SNPs and fourteen haplotypes were identified in five regions of GS3 genes. The detection of multiple candidate genes/QTLs within the candidate interval is beneficial for further excavation of superior rice genetic resources.

The OsCLV2s-OsCRN1 co-receptor regulates grain shape in rice

The highly conserved CLV–WUS negative feedback pathway plays a decisive role in regulating stem cell maintenance in shoot and floral meristems in higher plants,including Arabidopsis,rice,maize,and tomato.Here,we find significant natural variations in the OsCLV2c,OsCLV2d,and OsCRN1 loci in a genome-wide association study of grain shape in rice.OsCLV2a,OsCLV2c,OsCLV2d,and OsCRN1 negatively regulate grain length–width ratio and show distinctive geographical distribution,indica–japonica differentiation,and artificial selection signatures.Notably,OsCLV2a and OsCRN1 interact biochemically and genetically,suggesting that the two components function in a complex to regulate grain shape of rice.Furthermore,the genetic contributions of the haplotypes combining OsCLV2a,OsCLV2c,and OsCRN1 are significantly higher than those of each single gene alone in controlling key yield traits.These findings identify two groups of receptor-like kinases that may function as distinct co-receptors to control grain size in rice,thereby revealing a previously unrecognized role of the CLV class genes in regulating seed development and proposing a framework to understand the molecular mechanisms of the CLV–WUS pathway in rice and other crops.

TaACTIN7-D regulates plant height and grain shape in bread wheat

Exploitation of new gene resources and genetic networks contributing to the control of crop yield-related traits,such as plant height,grain size,and shape,may enable us to breed modern high-yielding wheat varieties through molecular methods.In this study,via ethylmethanesulfonate mutagenesis,we identify a wheat mutant plant,mu-597,that shows semi-dwarf plant architecture and round grain shape.Through bulked segregant RNA-seq and map-based cloning,the causal gene for the semi-dwarf phenotype of mu-597 is located.We find that a single-base mutation in the coding region of TaACTIN7-D(TaACT7-D),leading to a Gly-to-Ser(G65S)amino acid mutation at the 65th residue of the deduced TaACT7-D protein,can explain the semi-dwarfism and round grain shape of mu-597.Further evidence shows that the G65S mutation in TaACT7-D hinders the polymerization of actin from monomeric(G-actin)to filamentous(F-actin)status while attenuates wheat responses to multiple phytohormones,including brassinosteroids,auxin,and gibberellin.Together,these findings not only define a new semi-dwarfing gene resource that can be potentially used to design plant height and grain shape of bread wheat but also establish a direct link between actin structure modulation and phytohormone signal transduction.

One size does not fit all: Refining zircon provenance interpretations via integrated grain shape, geochronology, and Hf isotope analysis

Sediment provenance studies commonly utilize isotopic signatures to resolve detrital mineral sources and routing.However,non-unique ages and geochemical characteristics across geographically distinct crystalline source regions can lead to significant ambiguities in mineral provenance interpretations.Such ambiguity is apparent in southern Australia’s Cenozoic Eucla Basin,which hosts world-class heavy mineral sand resources.Here,new Hf isotope data are provided from four heavy mineral prospects(N=8,n=844[N=samples,n=grains]).Zircon grain shape data are also presented for a suite of detrital Eucla Basin samples(N=22,n=35,604)and the basin’s underlying basement,the Coompana Province(N=13,n=824).The data are integrated with published detrital and non-detrital primary zircon data to investigate the efficacy of grain shape analysis to better resolve the basin’s mineral provenance.Zircon Hf isotope compositions indicate a primary Mesoproterozoic juvenile source for zircon melts(~1250-1000 Ma,-2.5<εHf>~+5)with additional contributions from a range of juvenile to evolved late Archean to Phanerozoic-aged zircon bearing magmas(-28.0<εHf>+11).U-Pb geochronology and Hf isotopes are incapable of differentiating Mesoproterozoic-aged source rocks bounding the region for the majority of heavy mineral deposits analyzed as potential sources express overlapping crystallization ages and similarities in Hf-isotope characteristics.However,distinct zircon grain shapes(i.e.,perimeter,major axis and circularity)facilitate improved differentiation across these Mesoproterozoic sources.Filtering of U-Pb age,Hf isotope and shape data implicate the underlying Madura and Coompana provinces as dominant sediment sources for Eucla Basin detritus aged~1400-1000 Ma.The lack of direct sediment pathways between the underlying basement provinces and placer sediments analyzed demonstrates the significance of zircon reworking from intermediate sedimentary basins in the formation of the economically significant Eucla Basin beach placers.Zircon grain shape represents a cheaply acquired and readily incorporated grain characteristic that can enhance provenance investigations.

OsDA1 positively regulates grain width in rice

The size and shape of rice grains influence their yield and commercial value.We investigated the role of OsDA1,a rice homolog of the Arabidopsis DA1 gene,in regulating grain size and shape.OsDA1 was highly expressed in young spikelets and glumes.Its overexpression led to enlarged seeds with increased width and decreased length/width ratio(LWR)and knocking out OsDA1 reduced grain width and increased grain length and LWR.A R310K point mutation in the DA1-like domain is a potential target for breeding for increased grain width and length.OsDA1 interacted with TCP gene-family proteins to regulate grain size and shape.Our findings deepen our understanding of the molecular mechanisms underlying grain size regulation and provide useful information for improving grain yield.

Evolution of grain size and grain shape during thermomechanical processing in a powder metallurgical nickel-based superalloy

With a strain rate range of 0.01–10 s^(−1) and a deformation temperature range of 1110–1200℃,the isothermal compression test was performed on one powder metallurgy superalloy which is macroscopic segregation free.Using electron backscatter diffraction,the effect of strain rate and deformation temperature on grain shape and grain size of superalloys during thermal deformation was studied.The results established that exquisite and equiaxed dynamic recrystallization(DRX)grains are procured at supernal deformation temperature and high strain rate because of the high dislocation density.At the same time,the interaction between high DRX nucleation rate and low grain growth rate at high strain rate is favorable in making finer DRX grains.The equivalent medial grain size expanded with lowering strain rate and elevating proof temperature.Moreover,the grain shape was researched by the effective method of aspect ratio.Most aspect ratio of original grains is 0.61,and the aspect ratio has important implications for DRX and grain growth process.The average aspect ratio increases slightly when deformation temperature rises from 1110 to 1140℃,while the average aspect ratio increases memorably as the deformation temperature is higher than 1140℃.

Dissecting the Genetic Basis of Extremely Large Grain Shape in Rice Cultivar 'JZ1560'

Rice grain shape, grain length （GL）, width （GW）, thickness （GT） and length-to-width ratio （LWR）, are usually controlled by multiple quantitative trait locus （QTL）. To elucidate the genetic basis of extremely large grain shape, QTL analysis was performed using an F2 population derived from a cross between a japonica cuttivar ＇JZI560＇ （extremely large grain） and a contrasting indica cultivar ＇FAZI＇ （small grain）. A total number of 24 QTLs were detected on seven different chromosomes. QTLs for GL, GW, GT and LWR explained 11.6%, 95.62%, 91.5% and 89.9% of total phenotypic variation, respectively. Many QTLs pleiotropically controlled different grain traits, contributing complex traits correlation. GW2 and qSW5/GW5, which have been cloned previously to control GW, showed similar chromosomal locations with qGW2-1/qGT2-1/qLWR2-2 and qGW5-2/qLWR5-1 and should be the right candidate genes. Plants pyramiding GW2 and qSW5/GW5 showed a significant increase in GW compared with those carrying one of the two major QTLs. Furthermore, no significant QTL interaction was observed between GW2 and qSW5/GW5. These results suggested that GW2 and qSW5/GW5 might work in independent pathways to regulate grain traits. ＇JZ1560＇ alleles underlying all QTLs contributed an increase in GW and GT and the accumulation of additive effects generates the extremely large grain shape in ＇JZ1560＇.

Dissecting the Genetic Basis of Grain Shape and Chalkiness Traits in Hybrid Rice Using Multiple Collaborative Populations

Dear Editor Through the efficient use of heterosis, hybrid rice varieties generally have higher grain yield potential than inbred varieties. With the significant advantage in grain yield, over the past 30 years approximately half of China＇s total rice-growing area is planted with rice hybrids. However, grain quality has now become one of the most important targets in hybrid rice breeding for meeting consumer demands. Grain shape and chalkiness are two important components of rice grain quality, in which slender grains （typically, grain length-to-width ratio 〉3） with low chatkiness are preferred by most consumers of hybrid rice.

Conditions of Incipient Motion of Pebbles Based on Shape and the Equivalent Grain Size

Incipient motion of pebbles is an unsteady and random process,the main influence factors are pebble shape,non-uniformity,location in bed and flow condition.By virtue of the concept of the equivalent grain size,it is shown that d_ηfollows a normal distribution following a regression analysis of measured data.Consid- ering the influence of pebble shape and the relative exposure degree,formula of calculating the incipient veloc- ity for pebbles is deduced based on the equivalent grain size of pebble and the...

Effects of aging treatment on the microstructure and superelasticity of columnar-grained Cu71Al18Mn11 shape memory alloy

The effect of aging treatment on the superelasticity and martensitic transformation critical stress in columnar-grained Cu_（71）Al_（18）Mn_（11） shape memory alloy（SMA） at the temperature ranging from 250°C to 400°C was investigated. The microstructure evolution during the aging treatment was characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results show that the plate-like bainite precipitates distribute homogeneously within austenitic grains and at grain boundaries. The volume fraction of bainite increases with the increase in aging temperature and aging time, which substantially improves the martensitic transformation critical stress of the alloy, whereas the bainite only slightly affects the superelasticity. This behavior is attributed to a coherent relationship between the bainite and the austenite, as well as to the bainite and the martensite exhibiting the same crystal structure. The variations of the martensitic transformation critical stress and the superelasticity of columnar-grained Cu_（71）Al_（18）Mn_（11） SMA with aging-temperature and aging time are described by the Austin-Rickett equation, where the activation energy of bainite precipitation is 77.2 kJ ·mol1. Finally, a columnar-grained Cu_（71）Al_（18）Mn_（11） SMA with both excellent superelasticity（5%-9%） and high martensitic transformation critical stress（443-677 MPa） is obtained through the application of the appropriate aging treatments.

Effects of microalloying on grain refinement behaviors and hardness properties of wedge-shaped Al-Mg-Mn castings

The effects of microalloying elements Ti,Sc,Zr and Er on grain refinement behaviors and hardness properties of wedge-shaped Al-Mg-Mn alloy castings were investigated. The results indicate that alloys containing Sc and Zr can remarkably reduce the grain sizes of Al-Mg-Mn castings. Combination of Sc,Zr and Er can completely eliminate the columnar dendritic grains and further obtain refined grains with nondendritic sub-structure;the whole wedge-shaped cross-section of the casting consequently exhibits more homogeneous cast structures instead of the typical tri-crystal region structures. Large amounts of Al3Sc-based intermetallic compound particles,such as Al3(Sc1-x,Zrx),Al3(Sc1-x,Tix),Al3(Sc1-x-y,Zrx,Tiy) and Al3(Sc1-x-y,Zrx,Ery) are present in the microalloyed alloys,resulting from their numerously forming in high-temperature melt before solidification. These phases have the same L12-type crystal structure to Al3Sc phase as well as smaller misfits with the primary α(Al) grains,which leads to more efficient epitaxial growth for α(Al) grains on all crystal planes of these composite phases. The experimental alloys have been hardened in different levels and,show the low susceptibilities of hardness change with varying cooling rate. The high hardness of the castings are caused by grain-refined strengthening and solid solution strengthening.

EBSD Analysis of the Submicron Width Fibber Shaped Grain Copper Fabricated by Drawing

Several drawing processes of 3N pure copper (Cu) with ultra high reduction in area have been performed, and the texture has been observed using electron back scattered diffraction. It is well known that the texture of drawn Cu is closely related to its mechanical properties;in particular nanometer scale width fibber shaped grain is interesting. Previously, it was reported that drawing 3N Cu with around 95% reduction in area changes its mechanical properties. In the present experiment, grains have been changed from round to fiber-shaped, and subsequently, submicron-width fiber grains were generated with a 94.546% reduction in area. However, above 94.546% reduction in area, dynamic recrystallization occurred and then, prevented the grains to be finer. Further recrystallized grains influence on the macroscopic mechanical properties of Cu wire. Furthermore, the distribution of the misorientation angle at grain boundaries increased with an increase in the degree of reduction in area;in particular, the distribution drastically increased between 94.546% and 99.997%. Further, the frequency of coincidence of site lattice boundaries increased. The abovementioned variations in texture are closely related to mechanical properties.