The environment,especially the minimum temperature,affects summer maize grain yield by regulating ear differentiation and grain development

Ear differentiation,grain development and their interaction with factors in the growing environment,such as temperature,solar radiation and precipitation,greatly influence grain number and grain weight,and ultimately affect summer maize production.In this study,field experiments involving different sowing dates were conducted over three years to evaluate the effects of temperature factors,average solar radiation and total precipitation on the growth process,ear differentiation,fertilization characteristics,grain filling and yield of summer maize varieties with different growth durations.Four hybrids were evaluated in Huang-Huai-Hai Plain(HHHP),China from 2018 to 2020 with five different sowing dates.The results showed that the grain yield formation of summer maize was strongly impacted by the environment from the silking(R1)to milking(R3)stage.Average minimum temperature(AT_(min))was the key environmental factor that determined yield.Reductions in the length of the growing season(r=–0.556,P<0.01)and the total floret number on ear(R^(2)=0.200,P<0.001)were found when AT_(min) was elevated from the emerging(VE)to R1 stage.Both grain-filling rate(R^(2)=0.520,P<0.001)and the floret abortion rate on ear(R^(2)=0.437,P<0.001)showed quadratic relationships with AT_(min) from the R1 to physiological maturity(R6)stage,while the number of days after the R1 stage(r=–0.756,P<0.01)was negatively correlated with AT_(min).An increase in AT_(min) was beneficial for the promotion of yield when it did not exceeded a certain level(above 23°C during the R1–R3 stage and 20–21°C during the R1-R6 stage).Enhanced solar radiation and precipitation during R1–R6 increased the grain-filling rate(R^(2)=0.562,P<0.001 and R^(2)=0.229,P<0.05,respectively).Compared with short-season hybrids,full-season hybrids showed much greater suitability for a critical environment.The coordinated regulation of AT_(min),ear differentiation and grain development at the pre-and post-silking stages improved maize yield by increasing total floret number and grain-filling rate,and by reducing the floret abortion rate on ear.

Polyamines in developing rice grains and their relations with grain filling

Many studies have reported that polyamines have an effect on a number of growth and developmental process in plants, such as cell division, embryogenesis, senescense, and flowering. However, there are few reports on the physiological significance in of polyamines grain filling of rice. We studied the level of polyamines in the developing grains and their relations with grain filling and grain weight, using 8 rice varieties including hybrid combinations. It was showed that the content of Put (puterscine), Spd (spermidine), and Spm (spermine), especially Spd and Spm, was

Correlation Analysis of Rice Seed Setting Rate and Weight of 1 000-Grain and Agro-Meteorology over the Middle and Lower Reaches of the Yangtze River,China

The purpose of this study is to reveal the effects of historic climate change on rice yield over the middle and lower reaches of the Yangtze River, China, and to better adapt to climate change in the future. This study presents the relation of temperature and precipitation and rice components from 1981 to 2003 at 48 early rice stations and 30 middle rice stations. It focuses on an analysis of three stages： flowering, pre-milk, and late milk. The results show that mean maximum temperature and mean daily precipitation at the stages of flowering and pre-milk are most related to early rice yield. Yield change of middle rice is mainly because of mean precipitation change at the flowering stage. Furthermore, percentage of undeveloped grain increases as mean maximum temperature rises at the flowering stage. Over-precipitation in the reproductive stage is a major reason for reduction in yield of early rice. Consecutive rainfall and continuous high temperature can have negative effects on middle rice yield. Global warming would affect middle rice more seriously than early rice.

Comparisons of Metabolic Profiles for Carbohydrates,Amino Acids,Lipids,Fragrance and Flavones During Grain Development in indica Rice Cultivars

We used a widely targeted metabolomics approach to examine the metabolic changes in three pedigreed indica cultivars(Meixiangzhan 2,Meisizhan and Qixinzhan),with different eating qualities,at 8,15 and 30 d after flowering(DAF)to explore the formation mechanism of rice eating and nutritional qualities at a global metabolic level.A total of 623 metabolites were identified,and results showed that metabolic variations among rice cultivars decreased with grain developmental stage,suggesting that sufficient carbohydrate and amino acid supply during grain development may contribute to excellent rice eating and nutritional quality formation.Lysophosphatidylcholines 19:0 and 16:1 were beneficial for excellent eating quality formation during grain development.Rice fragrance was attributed mainly to spermidine andγ-aminobutyric acid.Rice cultivars with excellent eating quality at 15-30 DAF had relatively higher flavone content,possibly because they had adequate carbohydrate and amino acid contents during grain development.These results provided insight into the mechanisms for establishing rice eating and nutritional qualities during grain formation at a global metabolic level,and can be applied towards improving rice quality.

Grain proteomic analysis reveals central stress responsive proteins caused by wheat-Haynaldia villosa 6VS/6AL translocation

Haynaldia villosa(2n=14,VV),a wild grass of the subtribe Triticeae,serves as potential gene resources for wheat genetic improvement.In this study,the proteome characterization during grain development of Yangmai 5 and Yangmai 5-H.villosa 6VS/6AL translocation line was investigated by a comparative proteomic approach.Two-dimensional electrophoresis identified 81 differentially accumulated proteins(DAPs)during five grain developmental stages in wheat-H.villosa translocation line.These proteins were mainly involved in stress defense,storage protein,energy metabolism,protein metabolism and folding,carbon metabolism,nitrogen metabolism,and starch metabolism.In particular,6VS/6AL translocation led to significant upregulation of 36 DAPs and specific expression of 11 DAPs such as chitinase,thaumatin-like proteins,glutathione transferase,α-amylase inhibitor,heat shock proteins,and betaine aldehyde dehydrogenase.These proteins mainly involved in biotic and abiotic stress responses.Further analysis found that the upstream 1500 promoter regions of these stress-responsive DAP genes contained multiple high-frequency cis-acting elements related to stress defense such as abscisic acid response element ABRE,methyl jasmonate(MeJA)-response element TGACG-motif and CGTCA-motif involved in oxidative stress and antioxidant response element(ARE).RNA-seq and RT-qPCR analyses revealed the high expression of these stress-defensive DAP genes in the developing grains,particularly at the early-middle grain filling stages.Our results demonstrated that 6VS chromosome of H.villosa contains abundant stress-defensive proteins that have potential values for wheat genetic improvement.

Chromatin accessibility landscapes revealed the subgenome-divergent regulation networks during wheat grain development

Development of wheat(Triticum aestivum L.)grain mainly depends on the processes of starch synthesis and storage protein accumulation,which are critical for grain yield and quality.However,the regulatory network underlying the transcriptional and physiological changes of grain development is still not clear.Here,we combined ATAC-seq and RNA-seq to discover the chromatin accessibility and gene expression dynamics during these processes.We found that the chromatin accessibility changes are tightly associated with differential transcriptomic expressions,and the proportion of distal ACRs was increased gradually during grain development.Specific transcription factor(TF)binding sites were enriched at different stages and were diversified among the 3 subgenomes.We further predicted the potential interactions between key TFs and genes related with starch and storage protein biosynthesis and found different copies of some key TFs played diversified roles.Overall,our findings have provided numerous resources and illustrated the regulatory network during wheat grain development,which would shed light on the improvement of wheat yields and qualities.

GRAIN INCOMPLETE FILLING 2 regulates grain filling and starch synthesis during rice caryopsis development

Rice grain filling determines grain weight, final yield and grain quality. Here, a rice defective grain filling mutant, gif2, was identified. Grains ofgif2 showed a slower filling rate and a significant lower final grain weight and yield compared to wild-type. The starch content in gilt2 was noticeably decreased and its physicochemical properties were also altered. Moreover, gif2 endosperm cells showed obvious defects in compound granule formation. Posi- tional cloning identified GIF2 to encode an ADP-glucose pyrophosphorylase （AGP） large subunit, AGPL2; consequently, AGP enzyme activity in gif2 endosperms was remarkably decreased. GIF2 is mainly expressed in developing grains and the coded protein localizes in the cytosol. Yeast two hybrid assay showed that GIF2 interacted with AGP small subunits OsAGPS% OsAGPS2a and OsAGPS2b. Transcript levels for granule-bound starch synthase, starch synthase, starch branching enzyme and starch debranching enzyme were distinctly elevated in gif2 grains. In addition, the level of nucleotide diversity of the GIF2 locus was extremely low in both cultivated and wild rice. All of these results suggest that GIF2 plays important roles in the regulation of grain filling and starch biosynthesis during caryopsis development, and that it has been preserved during selection throughout domestication of modern rice.

Ubiquitinome Profiling Reveals the Landscape of Ubiquitination Regulation in Rice Young Panicles

Ubiquitination,an essential post-transcriptional modification(PTM),plays a vital role in nearly every biological process,including development and growth.Despite its functions in plant reproductive development,its targets in rice panicles remain unclear.In this study,we used proteome-wide profiling of lysine ubiquitination in rice(O.sativa ssp.indica)young panicles.We created the largest ubiquitinome dataset in rice to date,identifying 1638 lysine ubiquitination sites on916 unique proteins.We detected three conserved ubiquitination motifs,noting that acidic glutamic acid(E)and aspartic acid(D)were most frequently present around ubiquitinated lysine.Enrichment analysis of Gene Ontology(GO)annotations and Kyoto Encyclopedia of Genes and Genomes(KEGG)pathways of these ubiquitinated proteins revealed that ubiquitination plays an important role in fundamental cellular processes in rice young panicles.Interestingly,enrichment analysis of protein domains indicated that ubiquitination was enriched on a variety of receptorlike kinases and cytoplasmic tyrosine and serine-threonine kinases.Furthermore,we analyzed the crosstalk between ubiquitination,acetylation,and succinylation,and constructed a potential protein interaction network within our rice ubiquitinome.Moreover,we identified ubiquitinated proteins related to pollen and grain development,indicating that ubiquitination may play a critical role in the physiological functions in young panicles.Taken together,we reported the most comprehensive lysine ubiquitinome in rice so far,and used it to reveal the functional role of lysine ubiquitination in rice young panicles.

OPAQUE3, encoding a transmembrane bZIP transcription factor, regulates endosperm storage protein and starch biosynthesis in rice

Starch and storage proteins are the main components of rice(Oryza sativa L.)grains.Despite their importance,the molecular regulatory mechanisms of storage protein and starch biosynthesis remain largely elusive.Here,we identified a rice opaque endosperm mutant,opaque3(o3),that overaccumulates 57-kDa proglutelins and has significantly lower protein and starch contents than the wild type.The o3 mutant also has abnormal protein body structures and compound starch grains in its endosperm cells.OPAQUE3(O3)encodes a transmembrane basic leucine zipper(bZIP)transcription factor(OsbZIP60)and is localized in the endoplasmic reticulum(ER)and the nucleus,but it is localized mostly in the nucleus under ER stress.We demonstrated that O3 could activate the expression of several starch synthesis-related genes(GBSSI,AGPL2,SBEI,and ISA2)and storage protein synthesis-related genes(OsGluA2,Prol14,and Glb1).O3 also plays an important role in protein processing and export in the ER by directly binding to the promoters and activating the expression of OsBIP1 and PDIL1-1,two major chaperones that assist with folding of immature secretory proteins in the ER of rice endosperm cells.High-temperature conditions aggravate ER stress and result in more abnormal grain development in o3 mutants.We also revealed that OsbZIP50 can assist O3 in response to ER stress,especially under high-temperature conditions.We thus demonstrate that O3 plays a central role in rice grain development by participating simultaneously in the regulation of storage protein and starch biosynthesis and the maintenance of ER homeostasis in endosperm cells.