Effect of genetic distances of different genotypes of maize on the authenticity of single seeds detected by NIR spectroscopy.

Introduction: NIR spectroscopy combined with chemometric algorithms has been widely used for seed authenticity detection. However, the study of seed genetic distance, an internal feature that affects the discriminative performance of classification models, has rarely been reported. Methods: Therefore, maize seed samples of different genotypes were selected to investigate the effect of genetic distance on the authenticity of single seeds detected by NIR spectroscopy. Firstly, the Support vector machine (SVM) model was established using spectral information combined with a preprocessing algorithm, and then the DNA of the samples was extracted to study the correlation between genetic and relative spectral distances, the model identification performance, and finally to compare the similarities and differences between the results of genetic clustering and relative spectral clustering. Results: The results were as follows: the average accuracy of the models was 93.6% (inbred lines) and 93.7% (hybrids), respectively; Genetic distance and correlation spectral distance exhibited positive correlation significantly (inbred lines: r=0.177, p<0.05; hybrids: r=0.238, p<0.05), likewise genetic distance and model accuracy also showed positive correlation (inbred lines: r=0.611, p<0.01; hybrids: r=0.6158, p<0.01); Genetic clustering and spectral clustering results were essentially uniform for 94.3% (inbred lines) and 93.9% (hybrids), respectively. Discussion: This study reveals the relationship between the genetic and relative spectral distances of seeds and the accuracy of the model, which provides theoretical basis for the establishment of the standardized system for detecting the authenticity of seeds by NIR spectroscopic techniques.

14-3-3 proteins regulate photomorphogenesis by facilitating light-induced degradation of PIF3.

14-3-3s are highly conserved phosphopeptide-binding proteins that play important roles in various developmental and signaling pathways in plants. However, although protein phosphorylation has been proven to be a key mechanism for regulating many pivotal components of the light signaling pathway, the role of 14-3-3 proteins in photomorphogenesis remains largely obscure. PHYTOCHROME-INTERACTING FACTOR3 (PIF3) is an extensively studied transcription factor repressing photomorphogenesis, and it is well-established that upon red (R) light exposure, photo-activated phytochrome B (phyB) interacts with PIF3 and induces its rapid phosphorylation and degradation. PHOTOREGULATORY PROTEIN KINASES (PPKs), a family of nuclear protein kinases, interact with phyB and PIF3 in R light and mediate multisite phosphorylation of PIF3 in vivo. Here, we report that two members of the 14-3-3 protein family, 14-3-3λ and κ, bind to a serine residue in the bHLH domain of PIF3 that can be phosphorylated by PPKs, and act as key positive regulators of R light-induced photomorphogenesis. Moreover, 14-3-3λ and κ preferentially interact with photo-activated phyB and promote the phyB-PIF3-PPK complex formation, thereby facilitating phyB-induced phosphorylation and degradation of PIF3 upon R light exposure. Together, our data demonstrate that 14-3-3λ and κ work in close concert with the phyB-PIF3 module to regulate light signaling in Arabidopsis.

Seed Vigour and Morphological and Physiological Characteristics of Epimedium brevicornu Maxim: In Different Stages of Seed Development.

Epimedium brevicornu Maxim is a traditional Chinese medicinal plant with important value for curing several diseases, including liver cancer. Seed germination, field seedling emergence, and morphological and physiological traits were measured in developing seeds of E. brevicornu, which were collected at 7, 14, 21, 28, and 35 days after flowering. The results showed that with the fruit pericarp changing from lime green to dark red, the seed volume increased. Furthermore, the dry mass of seeds gradually increased from 0.011 g at 7 d to 0.275 g at 35 d, which was a significantly positive correlation with seed vigour (r = 0.980). The soluble protein content initially increased and then decreased to 11.09 mg/g and presented a maximum at 28 d; however, the soluble sugar content gradually declined to a minimum of 30.45 mg/g at 35 d, which was also significantly negatively correlated with seed vigour (r = -0.915). Furthermore, the unsaturated fatty acids (oleic acid and linoleic acid) increase with seed development. Abscisic acid (ABA) reached a maximum value of 18.45 ng/g at 28 d, and gibberellin (GA3), 3-Indoleacetic acid (IAA) and zeatin-riboside (ZR) initially increased and then decreased. These results suggest that the vigour of E. brevicornu seeds is closely associated with their stage of development, with the highest vigour observed at 28~35 d after flowering.

Nondestructive in situ monitoring of pea seeds germination using optical coherence tomography.

Seed germination and uniform plant stand in the field are the most critical crop growth stages determining the final yield. Pea (Pisum sativum L.) seeds production is often hampered due to the seed dormancy caused by the hard seed coat. Such effect is mainly attributed to poor or uneven germination and unsynchronised seedling emergence. Understanding the time course of water intake and several critical germination indicators can reveal many features of seed germination such as rate and uniformity. This paper used optical coherence tomography (OCT), a noninvasive and cross-sectional imaging technique, to monitor the inner structural changes throughout the germination process. A sequence of cross-sectional OCT images of pea (P. sativum L.) seeds, together with additional microscopic optical images, was recorded continuously and in situ for over 40 h. OCT and microscopic images revealed the changes in the internal structure and the external shape of the pea seeds during germination, respectively. It was found that the cross-sectional OCT images helped to identify the critical indicators distinguishing the different phases of germination pea seeds. Therefore, the presented OCT approach offers a fast and nondestructive way to precisely measure the structural indicators in different germination phases.

HTPdb and HTPtools: Exploiting maize haplotype-tag polymorphisms for germplasm resource analyses and genomics-informed breeding.

Along with rapid advances in high-throughput-sequencing technology, the development and application of molecular markers has been critical for the progress that has been made in crop breeding and genetic research. Desirable molecular markers should be able to rapidly genotype tens of thousands of breeding accessions with tens to hundreds of markers. In this study, we developed a multiplex molecular marker, the haplotype-tag polymorphism (HTP), that integrates Maize6H-60K array data from 3,587 maize inbred lines with 6,375 blocks from the recombination block map. After applying strict filtering criteria, we obtained 6,163 highly polymorphic HTPs, which were evenly distributed in the genome. Furthermore, we developed a genome-wide HTP analysis toolkit, HTPtools, which we used to establish an HTP database (HTPdb) covering the whole genomes of 3,587 maize inbred lines commonly used in breeding. A total of 172,921 non-redundant HTP allelic variations were obtained. Three major HTPtools modules combine seven algorithms (e.g., chain Bayes probability and the heterotic-pattern prediction algorithm) and a new plotting engine named "BCplot" that enables rapid visualization of the background information of multiple backcross groups. HTPtools was designed for big-data analyses such as complex pedigree reconstruction and maize heterotic-pattern prediction. The HTP-based analytical strategy and the toolkit developed in this study are applicable for high-throughput genotyping and for genetic mapping, germplasm resource analyses, and genomics-informed breeding in maize.

Field Screening of Rice Germplasm (Oryza sativa L. ssp. japonica) Based on Days to Flowering for Drought Escape.

Terminal drought stress is one of the restrictive factors in rice production and is expected to upsurge under the current situation of climate change. The study evaluated the performance of 2030 rice genotypes under continuous drought stress conditions based on days to flowering (DF). The genotypes under augmented randomized complete block design were sown in May/June of 2017 and 2018 in the field with movable rainout that resulted in huge genetic diversity among the accessions. Descriptive statistics confirmed clear variation among accessions on growth duration, plant height to leaf, plant height to panicle, and germination percentage. Correlation, chemometric, and agglomerative hierarchical cluster analyses were performed that categorized the germplasm into 10 groups. Genotypes in clusters VIII and IX (drought-resistant) revealed better agronomic performance in terms of reduced days to flowering, but conversely taller plant height and higher maturity (%) under severe stress. Genotypes in clusters IV, V, and X were discovered to be drought-susceptible. The screened genotypes like Longjing 12, Longdun 102, Yanjing 22, Liaojing 27, Xiaohongbandao, Songjing 17, and Zaoshuqingsen can be utilized in rice breeding improvement programs for drought tolerance in terms of severe continuous drought, as well as terminal drought stress.

The cold response regulator CBF1 promotes Arabidopsis hypocotyl growth at ambient temperatures.

Light and temperature are two core environmental factors that coordinately regulate plant growth and survival throughout their entire life cycle. However, the mechanisms integrating light and temperature signaling pathways in plants remain poorly understood. Here, we report that CBF1, an AP2/ERF-family transcription factor essential for plant cold acclimation, promotes hypocotyl growth under ambient temperatures in Arabidopsis. We show that CBF1 increases the protein abundance of PIF4 and PIF5, two phytochrome-interacting bHLH-family transcription factors that play pivotal roles in modulating plant growth and development, by directly binding to their promoters to induce their gene expression, and by inhibiting their interaction with phyB in the light. Moreover, our data demonstrate that CBF1 promotes PIF4/PIF5 protein accumulation and hypocotyl growth at both 22°C and 17°C, but not at 4°C, with a more prominent role at 17°C than at 22°C. Together, our study reveals that CBF1 integrates light and temperature control of hypocotyl growth by promoting PIF4 and PIF5 protein abundance in the light, thus providing insights into the integration mechanisms of light and temperature signaling pathways in plants.

QTL mapping analysis of maize plant type based on SNP molecular marker.

In this study, the elite maize inbred line (Zheng683-1) was used as a recurrent parent and the four maize inbred lines (ZPH1388, ZPH5, Dong 237 and Chang 7-2) were used as donor parents. The four F1 hybrids were produced by crossing between them and were continued backcrossing to the recurrent parent to produce four BC3F1s. The BC3F1 were pollinated by selfing four generations to generate the recombinant inbred lines (BC3F5) that showed variation in plant height, ear height, leaf angle. There were 53 lines for Zheng683-1 x ZPH1388, 53 lines for Zheng683-1 x ZPH5, 48 lines for Zheng683-1 x Dong237 and 61 lines for Zheng683-1 x Chang 7-2. The four populations were genotyped by using SNP marker and identified the QTLs of targeted traits by using QTL IciMapping V4.1 software and stepwise regression analysis. The main results are as follows:1. 19 additive QTLs and 2 dominant QTLs about plant height were detected in four introgression lines, and 7, 4, 5, 5 QTLs related plant height in ZPH1388-IL, ZPH5-IL, Dong237-ILand Chang7-2-IL. Among the 21 plant height QTLs, the largest contribution to phenotypic variation was QTLqPHa12 from Dong237-IL population, which evaluated 43.44% of the phenotypic variation of plant height . Followed by qPHa3 from ZPH1388-IL, the phenotypic contribution rate was 20% 2. Sixteen QTLs related ear height were detected in the population of the 4 introgression lines, of which there were 15 additive and 1 dominant QTLs. In addition, 9, 3, and 4 QTLs were detected in ZPH1388-IL, ZPH5-IL and Dong237-IL respectively. Among the 16 ear height QTLs, the largest contribution to phenotypic variation was QTL (qEHa1) from the ZPH1388 IL, which recorded the phenotypic variation of ear height by 26.01%. Next the phenotype contribution rates were 22.05% and 21.46%, respectively for qEHa13 and qEHa15 from Dong237-IL. Fourteen QTLs related leaf angle was detected in the population of the introgression lines, of which there were 5 additive QTLs and 9 dominant QTLs. Moreover, 2, 9, and 3 QTLs were detected in ZPH1388-IL, ZPH5-IL, Dong237-IL, respectively. Among the 14 leaf angle QTLs, the largest contribution to phenotypic variation was QTL (qLAa4) from the Dong237-IL then qLAa3 from ZPH5-IL, detecting the phenotypic variation of leaf angle of 28.56% and 24.08%,  respectively.The results showed that the QTL locus was characterized by uneven chromosome distribution. The chromosome 1, 2, 5, and 7 are the regions with the QTL concentrated distribution of plant type traits. The QTL of plant type also showed QTL concentrated distribution in some regions of chromosomes. For example, there are three QTLs about plant height and ear height in the region of chromosome bin1.02, three QTLs about plant and ear heights, as well as leaf angle in the region of chromosome bin 2.02. These areas are QTL enrichment region (or the hot spots) of the pleiotropic gene loci related the plant type and ear traits.

TANDEM ZINC-FINGER/PLUS3 Is a Key Component of Phytochrome A Signaling.

Phytochrome A (phyA) is the primary plant photoreceptor responsible for perceiving and mediating various responses to far-red (FR) light and is essential for survival in canopy shade. In this study, we identified two Arabidopsis thaliana mutants that grew longer hypocotyls in FR light. Genetic analyses showed that they were allelic and their FR phenotypes were caused by mutations in the gene named TANDEM ZINC-FINGER/PLUS3 (TZP), previously shown to encode a nuclear protein involved in blue light signaling and phyB-dependent regulation of photoperiodic flowering. We show that the expression of TZP is dramatically induced by light and that TZP proteins are differentially modified in different light conditions. Furthermore, we show that TZP interacts with both phyA and FAR-RED ELONGATED HYPOCOTYL1 (FHY1) and regulates the abundance of phyA, FHY1, and ELONGATED HYPOCOTYL5 proteins in FR light. Moreover, our data indicate that TZP is required for the formation of a phosphorylated form of phyA in the nucleus in FR light. Together, our results identify TZP as a positive regulator of phyA signaling required for phosphorylation of the phyA photoreceptor, thus suggesting an important role of phosphorylated phyA in inducing the FR light response.

The COP9 Signalosome regulates seed germination by facilitating protein degradation of RGL2 and ABI5.

The control of seed germination and seed dormancy are critical for the successful propagation of plant species, and are important agricultural traits. Seed germination is tightly controlled by the balance of gibberellin (GA) and abscisic acid (ABA), and is influenced by environmental factors. The COP9 Signalosome (CSN) is a conserved multi-subunit protein complex that is best known as a regulator of the Cullin-RING family of ubiquitin E3 ligases (CRLs). Multiple viable mutants of the CSN showed poor germination, except for csn5b-1. Detailed analyses showed that csn1-10 has a stronger seed dormancy, while csn5a-1 mutants exhibit retarded seed germination in addition to hyperdormancy. Both csn5a-1 and csn1-10 plants show defects in the timely removal of the germination inhibitors: RGL2, a repressor of GA signaling, and ABI5, an effector of ABA responses. We provide genetic evidence to demonstrate that the germination phenotype of csn1-10 is caused by over-accumulation of RGL2, a substrate of the SCF (CRL1) ubiquitin E3 ligase, while the csn5a-1 phenotype is caused by over-accumulation of RGL2 as well as ABI5. The genetic data are consistent with the hypothesis that CSN5A regulates ABI5 by a mechanism that may not involve CSN1. Transcriptome analyses suggest that CSN1 has a more prominent role than CSN5A during seed maturation, but CSN5A plays a more important role than CSN1 during seed germination, further supporting the functional distinction of these two CSN genes. Our study delineates the molecular targets of the CSN complex in seed germination, and reveals that CSN5 has additional functions in regulating ABI5, thus the ABA signaling pathway.

Maize Urb2 protein is required for kernel development and vegetative growth by affecting pre-ribosomal RNA processing.

Ribosome biogenesis is a fundamental process in eukaryotic cells. Although Urb2 protein has been implicated in ribosome biogenesis in yeast, the Urb2 domain is loosely conserved between plants and yeast, and the function of Urb2 protein in plants remains unknown. Here, we isolated a maize mutant, designated as urb2, with defects in kernel development and vegetative growth. Positional cloning and transgenic analysis revealed that urb2 encodes an Urb2 domain-containing protein. Compared with the wild-type (WT), the urb2 mutant showed decreased ratios of 60S/40S and 80S/40S and increased ratios of polyribosomes. The pre-rRNA intermediates of 35/33S rRNA, P-A3 and 18S-A3 were significantly accumulated in the urb2 mutant. Transcriptome profiling of the urb2 mutant indicated that ZmUrb2 affects the expression of a number of ribosome-related genes. We further demonstrated that natural variations in ZmUrb2 are significantly associated with maize kernel length. The overall results indicate that, by affecting pre-rRNA processing, the Urb2 protein is required for ribosome biogenesis in maize.

Identification of heterotic loci associated with grain yield and its components using two CSSL test populations in maize.

Heterosis has widely been used to increase grain yield and quality. In this study, the genetic basis of heterosis on grain yield and its main components in maize were examined over 2 years in two locations in two test populations constructed from a set of 184 chromosome segment substitution lines (CSSLs) and two inbred lines (Zheng58 and Xun9058). Of the 169 heterotic loci (HL) associated with grain yield and its five components identified in CSSL × Zheng58 and CSSL × Xun9058 test populations, only 25 HL were detected in both populations. The comparison of quantitative trait loci (QTLs) detected in the CSSL population with HL detected in the two test populations revealed that only 15.46% and 17.35% of the HL in the given populations respectively, shared the same chromosomal regions as that of the corresponding QTLs and showed dominant effects as well as pleiotropism with additive and dominant effects. In addition, most of the HL (74.23% and 74.49%) had overdominant effects. These results suggest that overdominance is the main contributor to the effects of heterosis on grain yield and its components in maize, and different HL are associated with heterosis for different traits in different hybrids.

[Detection of Adulteration in Milk Powder with Starch Near Infrared].

Three China trademarks of milk powder called Mengniu, Yili, Wandashan were taken as testing samples. Each of them mixed varied amount of starch in different gradient, which were consisted of 32 adulterated milk powder samples mixed with starch, was taken as standard samples for constructing predicted model. To those 32 samples, the reflecting spectrum characteristics in middle wave of near infrared spectrum with Near Infrared Spectrum Analyzer (Micro NIR 1700) produced by JDSU Ltd. USA were collected for five repeats in five different days. The time span was nearly two months. Firstly, we build the model used the reflecting spectrum characteristics of those samples with biomimetic pattern recognition (BPR) arithmetic to do the qualitative analysis. The analysis included the reliability of testing result and stability of the model. When we took ninety percent as the evaluation threshold of testing result of CAR (Correct Acceptance Rate) and CRR (Correct Rejection Rate), the lowest starch content of adulterate milk powder in all tested samples which the tested result were bigger than that abovementioned threshold was designated CAR threshold (CAR-T) and CRR threshold (CRR-T). CAR means the correct rate of accepting a sample which is belong to itself, CRR means correct rate of refusing to accept a sample which is not belong to itself. The results were shown that, when we constructed a model based on the near infrared spectrum data from each of three China trademark milk powders, respectively, if we constructed a model with infrared spectrum data tested in a same day, both the CAR-T and CRR-T of adulterate starch content of a sample can reach 0.1% in predicting the remainder infrared spectrum data tested within a same day. The three China trademarks of milk powder had the same result. In addition, when we ignored the trademarks, put the spectrum data of adulterate milk powder samples mixed with the same content of starch of three China trademarks milk powder together to construct a model, the CAR-T of mixed starch content of a sample may reach 0.1%, the CRR-T can reach 1%, if the model construction and predicting were performed with near infrared spectrum data tested in a same day. However, the CAR-T can just stably reach up to 5% and the CRR-T have the same result, if the model construction and predicting were crossly performed with mixed near infrared spectrum data tested in different days. Furthermore, the correct recognizing threshold mixed starch of a sample can stably reach up to 1% and the CAR-T can reach 5%, if the model construction was based on near infrared spectrum data combined the previous four days to predict the output of the another day. On the other hand, we also engaged quantitative analysis to the starch content in milk power with two kinds of arithmetic (PLSR, LS-SVR). In contrast with the testing outputs, the reliability of both the CAR-T and CRR-T in qualitative analysis was further validated.

Performance of hybrid progeny formed between genetically modified herbicide-tolerant soybean and its wild ancestor.

Gene flow from genetically modified (GM) crops to wild relatives might affect the evolutionary dynamics of weedy populations and result in the persistence of escaped genes. To examine the effects of this gene flow, the growth of F1 hybrids that were formed by pollinating wild soybean (Glycine soja) with glyphosate-tolerant GM soybean (G. max) or its non-GM counterpart was examined in a greenhouse. The wild soybean was collected from two geographical populations in China. The performance of the wild soybean and the F2 hybrids was further explored in a field trial. Performance was measured by several vegetative and reproductive growth parameters, including the vegetative growth period, pod number, seed number, above-ground biomass and 100-seed weight. The pod setting percentage was very low in the hybrid plants. Genetically modified hybrid F1 plants had a significantly longer period of vegetative growth, higher biomass and lower 100-seed weight than the non-GM ones. The 100-seed weight of both F1 and F2 hybrids was significantly higher than that of wild soybean in both the greenhouse and the field trial. No difference in plant growth was found between GM and non-GM F2 hybrids in the field trial. The herbicide-resistant gene appeared not to adversely affect the growth of introgressed wild soybeans, suggesting that the escaped transgene could persist in nature in the absence of herbicide use.

A rare SNP mutation in Brachytic2 moderately reduces plant height and increases yield potential in maize.

Plant height has long been an important agronomic trait in maize breeding. Many plant height QTLs have been reported, but few of these have been cloned. In this study, a major plant height QTL, qph1, was mapped to a 1.6kb interval in Brachytic2 (Br2) coding sequence on maize chromosome 1. A naturally occurring rare SNP in qph1, which resulted in an amino acid substitution, was validated as the causative mutation. QPH1 protein is located in the plasma membrane and polar auxin transport is impaired in the short near-isogenic line RIL88(qph1). Allelism testing showed that the SNP variant in qph1 reduces longitudinal cell number and decreases plant height by 20% in RIL88(qph1) compared to RIL88(QPH1), and is milder than known br2 mutant alleles. The effect of qph1 on plant height is significant and has no or a slight influence on yield in four F2 backgrounds and in six pairs of single-cross hybrids. Moreover, qph1 could reduce plant height when heterozygous, allowing it to be easily employed in maize breeding. Thus, a less-severe allele of a known dwarf mutant explains part of the quantitative variation for plant height and has great potential in maize improvement.

Characterization of a dwarf mutant allele of Arabidopsis MDR-like ABC transporter AtPGP1 gene.

Asymmetric auxin distribution caused by polar auxin transport (PAT) regulates many plant developmental and physiological processes. Plant two closely ABC (ATP-binding cassette) transporter, AtPGP1 and AtPGP19 (AtMDR1), have been implicated in auxin transport. However, unlike atpgp19 mutant and atpgp1 atmdr1 double mutant show decreased apical dominance, reduced growth, and impaired basipetal auxin transport, atpgp1 mutant exhibit no significant difference from wild type. We report a new allele of atpgp1 mutants, designated as atpgp1-2, which showed shorter hypocotyl and dwarf phenotype under long-day condition. Auxin transport activity was greatly impaired and NPA-sensitivity was decreased in the mutant. Moreover, we detected transcript in the atpgp1 mutants reported previously, but not in atpgp1-2. These results suggest a direct involvement of AtPGP1 in auxin transport processes controlling plant growth.

AtMYB14 Regulates Cold Tolerance in Arabidopsis.

Low temperature affects plant growth and crop productivity. The CBF genes are a class of transcription factors that play important roles in cold response. Here we report that AtMYB14 participates in freezing tolerance in Arabidopsis by affecting expression of CBF genes. The AtMYB14 gene was down-regulated by cold treatment. AtMYB14 encodes a nuclear protein that functions as an R2R3-MYB transcription activator. Knock-down of AtMYB14 by artificial microRNA increased the tolerance to freezing stress. Both the CBF genes and the downstream genes were induced to a much higher level in AtMYB14 knock-down plants than in wild type under cold treatment. Our results suggest that AtMYB14 plays an important role in the plant response to cold stress.

Seed coat microsculpturing is related to genomic components in wild Brassica juncea and Sinapis arvensis.

It has been reported that wild Brassica and related species are widely distributed across Xinjiang, China, and there has been an argument for species identification. Seed coat microsculpturing (SCM) is known to be an excellent character for taxonomic and evolutionary studies. By identifying collections from Xinjiang, China, and combining SCM pattern, flow cytometry, and genome-specific DNA markers as well as sexual compatibility with known species, this study aimed to detect potential relationships between SCM and genomic types in wild Brassica and related species. Three wild collections were found to be tetraploid with a SCM reticulate pattern similar to B. juncea, and containing A and B genome-specific loci, indicating relatively high sexual compatibility with B. juncea. The others were diploid, carrying S-genome-specific DNA markers, and having relatively high sexual compatibility with Sinapis arvensis. Moreover, their SCM was in a rugose pattern similar to that of S. arvensis. It was suggested that SCM, as a morphological characteristic, can reflect genomic type, and be used to distinguish B-genome species such as B. juncea from the related S. arvensis. The relationship between SCM and genomic type can support taxonomic studies of the wild Brassica species and related species.

The Arabidopsis anaphase-promoting complex/cyclosome subunit 1 is critical for both female gametogenesis and embryogenesis(F).

Anaphase-promoting complex/cyclosome (APC/C), a multisubunit E3 ligase, plays a critical role in cell cycle control, but the functional characterization of each subunit has not yet been completed. To investigate the function of APC1 in Arabidopsis, we analyzed four mutant alleles of APC1, and found that mutation in APC1 resulted in significantly reduced plant fertility, accumulation of cyclin B, and disrupted auxin distribution in embryos. The three mutant alleles apc1-1, apc1-2 and apc1-3 shared variable defects in female gametogenesis including degradation, abnormal nuclear number, and disrupted polarity of nuclei in the embryo sac as well as in embryogenesis, in which embryos were arrested at multiple stages. All of these defects are similar to those previously identified in apc4. The mutant apc1-4, in which the T-DNA was inserted after the transmembrane domain at the C-terminus, showed much more severe phenotypes; that is, most of the ovules were arrested at the one-nucleate female gametophyte stage (stage FG1). In the apc1 apc4 double mutants, the fertility was further reduced by one-third in apc1-1/+ apc4-1/+, and in some cases no ovules even survived in siliques of apc1-4/+ apc4-1/+. Our data thus suggest that APC1, an essential component of APC/C, plays a synergistic role with APC4 both in female gametogenesis and in embryogenesis.