Expression Of MADS-box Genes Research Articles

Morphological and expression analyses of MADS genes in Japanese traditional narrow- and/or staminoid-petaled cultivars of Rhododendron kaempferi Planch.

The morphological traits of the floral mutation cultivars ‘Kagaribi’, ‘Kinshibe’ and ‘Kin-kujyaku’ of Rhododendron kaempferi that characteristically exhibit extremely narrow and/or staminoid petals were investigated. In addition, to confirm the causes of the mutations in these cultivars, the MADS-box C class AG gene homologues in R. kaempferi were isolated, and the MADS-box gene expression patterns in the floral organs of the wild-type plants and cultivars were analyzed. A morphological observation of the epidermis showed that the ‘Kagaribi’ and ‘Kinshibe’ cultivars formed staminoid flag petals and staminoid organs in whorl 2, respectively. The epidermal cells of the staminoid organs of whorl 2 in ‘Kagaribi’ and ‘Kinshibe’ resembled those of the stamens in whorl 3. In ‘Kin-kujyaku,’ the petals in whorl 2 and leaves were extremely narrow. The sepals in whorl 1 were absent, and the style in whorl 4 was split into 5 parts. The epidermal cells of the petals in whorl 2 in ‘Kin-kujyaku’ were dissimilar to the epidermal cells of the stamens in whorl 3. The deduced amino acid sequence of the isolated AG homologue from R. kaempferi was well-conserved among the AG orthologues. The expression levels of RkAG in whorl 2 to whorl 3 of ‘Kagaribi’ and ‘Kinshibe’ was approximately 27% and the same level, respectively. In ‘Kin-kujyaku,’ the expression pattern was similar to that of the wild type. These results suggest that the ‘Kagaribi’ and ‘Kinshibe’ floral mutations might be caused by the expression of RkAG in whorl 2.

Effect of seed on ripening control components during avocado fruit development

Seedless avocado fruit are produced alongside seeded fruit in the cultivar Arad, and both reach maturity at the same time. Using this system, it was possible to show that avocado seed inhibits the ripening process: seedless fruits exhibited higher response to exogenous ethylene already at the fruitlet stage, and also at the immature and mature fruit stages. They produced higher CO 2 levels, and the ethylene peak was apparent at the fruitlet stage of seedless fruit, but not of seeded ones. The expression levels of PaETR, PaERS1 and PaCTR1 on the day of harvest at all developmental stages were very similar between seeded and seedless fruit, except that PaCTR1 was higher in seedless fruit only at very early stages. This expression pattern suggests that the seed does not have an effect on components of the ethylene response pathway when fruits are just picked. The expression of MADS-box genes, PaAG1 and PaAGL9, preceded the increase in ethylene production of mature seeded fruit, but not at earlier stages. However, only PaAGL9 was induced in seedless fruit at early stages of development. Taken together, these data suggest that these genes are perhaps involved in climacteric response in seeded fruit, and the seed is responsible for their induction at normal fruit ripening.

OsMADS6 plays an essential role in endosperm nutrient accumulation and is subject to epigenetic regulation in rice (Oryza sativa)

MADS-box transcription factors are known for their roles in plant growth and development. The regulatory mechanisms of spatial and temporal specific expression of MADS-box genes and the function of MADS-box genes in other biological processes are still to be explored. Here, we report that OsMADS6 is highly expressed in flower and endosperm in Oryza sativa (rice). In addition to displaying a homeotic organ identity phenotype in all the four whorls of the flowers, the endosperm development is severely affected in its mutant. At least 32% of the seeds lacked starch filling and aborted. For seeds that have starch filling and develop to maturity, the starch content is reduced by at least 13%. In addition, the seed shape changes from elliptical to roundish, and the protein content increases from 12.1 to 15.0% (P < 0.05). Further investigation shows that ADP-glucose pyrophosphorylase genes, encoding the rate-limiting step enzyme in the starch synthesis pathway, are subject to the regulation of OsMADS6. Chromatin immunoprecipitation (ChIP)-PCR analyses on the chromatin of the OsMADS6 gene find that H3K27 is trimethylated in tissues where OsMADS6 is silenced, and that H3K36 is trimethylated in tissues where OsMADS6 is highly activated. Point mutation analysis reveals that leucine at position 83 is critical to OsMADS6 function.

An Atlas of Type I MADS Box Gene Expression during Female Gametophyte and Seed Development in Arabidopsis

Members of the plant type I MADS domain subfamily have been reported to be involved in reproductive development in Arabidopsis (Arabidopsis thaliana). However, from the 61 type I genes in the Arabidopsis genome, only PHERES1, AGAMOUS-LIKE80 (AGL80), DIANA, AGL62, and AGL23 have been functionally characterized, which revealed important roles for these genes during female gametophyte and early seed development. The functions of the other genes are still unknown, despite the fact that the available single T-DNA insertion mutants have been largely investigated. The lack of mutant phenotypes is likely due to a considerable number of recent intrachromosomal duplications in the type I subfamily, resulting in nonfunctional genes in addition to a high level of redundancy. To enable a breakthrough in type I MADS box gene characterization, a framework needs to be established that allows the prediction of the functionality and redundancy of the type I genes. Here, we present a complete atlas of their expression patterns during female gametophyte and seed development in Arabidopsis, deduced from reporter lines containing translational fusions of the genes to green fluorescent protein and beta-glucuronidase. All the expressed genes were revealed to be active in the female gametophyte or developing seed, indicating that the entire type I subfamily is involved in reproductive development in Arabidopsis. Interestingly, expression was predominantly observed in the central cell, antipodal cells, and chalazal endosperm. The combination of our expression results with phylogenetic and protein interaction data allows a better identification of putative redundantly acting genes and provides a useful tool for the functional characterization of the type I MADS box genes in Arabidopsis.

Characterization of SQUAMOSA-like genes in Gerbera hybrida, including one involved in reproductive transition

BackgroundThe flowering process in plants proceeds through the induction of an inflorescence meristem triggered by several pathways. Many of the genes associated with both the flowering process and floral architecture encode transcription factors of the MADS domain family. Gerbera, a member of the sunflower family, Asteraceae, bears compressed inflorescence heads (capitula) with three different flower types characterized by differences in both sexuality and floral symmetry. To understand how such a complex inflorescence structure is achieved at the molecular level, we have characterized the array of Gerbera MADS box genes. The high number of SQUAMOSA-like genes in Gerbera compared to other model species raised the question as to whether they may relate to Gerbera's complex inflorescence structure and whether or not a homeotic A function is present.ResultsIn this paper we describe six Gerbera genes related to the SQUAMOSA/APETALA1/FRUITFULL genes of snapdragon and Arabidopsis. Based on phylogenetic analysis of the entire gene lineage, our data indicates that GSQUA1 and GSQUA3 are members of the SQUA/AP1 clade, while GSQUA2, GSQUA4, GSQUA5 and GSQUA6 are co-orthologs of the Arabidopsis FUL gene. GSQUA1/GSQUA3 and GSQUA4/GSQUA5/GSQUA6, respectively, represent several gene duplication events unknown in the model systems that may be specific to either Gerbera or Asteraceae. GSQUA genes showed specific expression profiles. GSQUA1, GSQUA2, and GSQUA5 were inflorescence abundant, while GSQUA3, GSQUA4, and GSQUA6 expression was also detected in vegetative organs. Overexpression of GSQUA2 in Gerbera led to accelerated flowering, dwarfism and vegetative abnormalities, all new and specific phenomena observed in transgenic Gerbera plants with modified MADS box gene expression.ConclusionsBased on expression patterns, none of the Gerbera SQUA-like genes are likely to control flower organ identity in the sense of the floral A function. However, our data shows that the FUL-like gene GSQUA2 plays a vital role in meristem transition. The roles of other GSQUA-genes in Gerbera floral development are intriguing, but require still further study.

The regulation of MADS-box gene expression during ripening of banana and their regulatory interaction with ethylene

Six MaMADS-box genes have been cloned from the banana fruit cultivar Grand Nain. The similarity of these genes to tomato LeRIN is low and neither MaMADS2 nor MaMADS1 complement the tomato rin mutation. Nevertheless, the expression patterns, specifically in fruit and the induction during ripening and in response to ethylene and 1-MCP, suggest that some of these genes may participate in ripening. MaMADS1, 2, and 3, are highly expressed in fruit only, while the others are expressed in fruit as well as in other organs. Moreover, the suites of MaMADS-box genes and their temporal expression differ in peel and pulp during ripening. In the pulp, the increase in MaMADS2, 3, 4, and 5 expression preceded an increase in ethylene production, but coincides with the CO2 peak. However, MaMADS1 expression in pulp coincided with ethylene production, but a massive increase in its expression occurred late during ripening, together with a second wave in the expression of MaMADS2, 3, and 4. In the peel, on the other hand, an increase in expression of MaMADS1, 3, and to a lesser degree also of MaMADS4 and 2 coincided with an increase in ethylene production. Except MaMADS3, which was induced by ethylene in pulp and peel, only MaMADS4, and 5 in pulp and MaMADS1 in peel were induced by ethylene. 1-MCP applied at the onset of the increase in ethylene production, increased the levels of MaMADS4 and MaMADS1 in pulp, while it decreased MaMADS1, 3, 4, and 5 in peel, suggesting that MaMADS4 and MaMADS1 are negatively controlled by ethylene at the onset of ethylene production only in pulp. Only MaMADS2 is neither induced by ethylene nor by 1-MCP, and it is expressed mainly in pulp. Our results suggest that two independent ripening programs are employed in pulp and peel which involve the activation of mainly MaMADS2, 4, and 5 and later on also MaMADS1 in pulp, and mainly MaMADS1, and 3 in peel. Hence, our results are consistent with MaMADS2, a SEP3 homologue, acting in the pulp upstream of the increase in ethylene production similarly to LeMADS-RIN.

Characterization, expression and function of DORMANCY ASSOCIATED MADS-BOX genes from leafy spurge

DORMANCY ASSOCIATED MADS-BOX (DAM) genes are related to AGAMOUS-LIKE 24 and SHORT VEGETATIVE PHASE genes of arabidopsis and are differentially regulated coordinately with endodormancy induction and release in buds of several perennial plant species. DAM genes were first shown to directly impact endodormancy in peach where a deletion of a series of DAM resulted in loss of endodormancy induction. We have cloned and characterized several MADS box genes from the model perennial weed leafy spurge. Leafy spurge DAM genes are preferentially expressed in shoot tips and buds in response to cold temperatures and day length in a manner that is relative to the level of endodormancy induced by various environmental conditions. Over-expression of one DAM gene in arabidopsis delays flowering. Additionally, we show that at least one DAM gene is differentially regulated by chromatin remodeling. Comparisons of the DAM gene promoters between poplar and leafy spurge have identified several conserved sequences that may be important for their expression patterns in response to dormancy-inducing stimuli.

A hitchhiker's guide to the MADS world of plants

Plant life critically depends on the function of MADS-box genes encoding MADS-domain transcription factors, which are present to a limited extent in nearly all major eukaryotic groups, but constitute a large gene family in land plants. There are two types of MADS-box genes, termed type I and type II, and in plants these groups are distinguished by exon-intron and domain structure, rates of evolution, developmental function and degree of functional redundancy. The type I genes are further subdivided into three groups - Mα, Mβ and Mγ - while the type II genes are subdivided into the MIKCC and MIKC* groups. The functional diversification of MIKCC genes is closely linked to the origin of developmental and morphological novelties in the sporophytic (usually diploid) generation of seed plants, most spectacularly the floral organs and fruits of angiosperms. Functional studies suggest different specializations for the different classes of genes; whereas type I genes may preferentially contribute to female gametophyte, embryo and seed development and MIKC*-group genes to male gametophyte development, the MIKCC-group genes became essential for diverse aspects of sporophyte development. Beyond the usual transcriptional regulation, including feedback and feed-forward loops, various specialized mechanisms have evolved to control the expression of MADS-box genes, such as epigenetic control and regulation by small RNAs. In future, more data from genome projects and reverse genetic studies will allow us to understand the birth, functional diversification and death of members of this dynamic and important family of transcription factors in much more detail.

Extended expression of B-class MADS-box genes in the paleoherb Asarum caudigerum

Asarum caudigerum (Aristolochiaceae) is a paleoherb species that is important for research in origin and evolution of angiosperm flowers due to its basal position in the angiosperm phylogeny. In this study, a subtracted floral cDNA library from floral buds of A. caudigerum was constructed and cDNA arrays by suppression subtractive hybridization were generated. cDNAs of floral buds at different stages before flower opening and of leaves at the seedling stage were used. The macroarray analyses of expression profiles of isolated floral genes showed that 157 genes out of the 612 unique ESTs tested revealed higher transcript abundance in the floral buds and uppermost leaves. Among them, 78 genes were determined to be differentially expressed in the perianth, 62 in the stamens, and 100 genes in the carpels. Quantitative real-time PCR of selected genes validated the macroarray results. Remarkably, APETALA3 (AP3) B-class genes isolated from A. caudigerum were upregulated in the perianth, stamens and carpels, implying that the expression domain of B-class genes in this basal angiosperm was broader than those in their eudicot counterparts.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-009-1048-6) contains supplementary material, which is available to authorized users.

Meristem activity during flower and ovule development in tomato is controlled by the mini zinc finger gene INHIBITOR OF MERISTEM ACTIVITY

Plants have the ability to form new organs as a result of indeterminate growth ensured by specific regions of pluripotent cells, called meristems. Flowers are produced by the activity of floral meristems which differ from vegetative meristems in their determinate fate. Transcriptional complexes associating C-, D- and E-type MADS box proteins are responsible for flower determinacy by controlling the stem cell population within the floral meristem. We report here that the INHIBITOR OF MERISTEM ACTIVITY (IMA) gene encoding a mini zinc finger (MIF) protein from tomato (Solanum lycopersicum) regulates the processes of flower and ovule development. IMA inhibits cell proliferation during floral termination, controls the number of carpels during floral development and acts as a repressor of the meristem organizing centre gene WUSCHEL. Underexpression of IMA prevents the formation of gametophytic tissue, which is replaced by an undetermined sporophytic tissue. Molecular analyses of MADS box gene expression revealed that IMA participates in the termination of floral meristems and initiation of ovule primordia by activating D-type gene expression. Taken together, our data indicate that both termination of floral meristems and differentiation of nucelli during ovule development require a similar mechanism involving the repression of WUSCHEL and the activation of D-class genes.

Overexpression of the cucumber LEAFY homolog CFL and hormone treatments alter flower development in gloxinia (Sinningia speciosa)

Leafy (LFY) and LFY-like genes control the initiation of floral meristems and regulate MADS-box genes in higher plants. The Cucumber-FLO-LFY (CFL) gene, a LFY homolog in Cucumis sativus L. is expressed in the primordia, floral primordia, and each whirl of floral organs during the early stage of flower development. In this study, functions of CFL in flower development were investigated by overexpressing the CFL gene in gloxinia (Sinningia speciosa). Our results show that constitutive CFL overexpression significantly promote early flowering without gibberellin (GA(3)) supplement, suggesting that CFL can serve functionally as a LFY homolog in gloxinia. Moreover, GA(3) and abscisic acid (ABA) treatments could modulate the expression of MADS-box genes in opposite directions. GA(3) resembles the overexpression of CFL in the expression of MADS-box genes and the regeneration of floral buds, but ABA inhibits the expression of MADS-box genes and flower development. These results suggest that CFL and downstream MADS-box genes involved in flower development are regulated by GA(3) and ABA.

Expression of the MADS-Box Gene &lt;I&gt;GmAGL15&lt;/I&gt; in Seed Development of Soybean

Expression of the MADS-Box Gene &lt;I&gt;GmAGL15&lt;/I&gt; in Seed Development of Soybean

MADS-box genes controlling inflorescence morphogenesis in sunflower

MADS-box genes play an important role in plant ontogeny, particularly, in the regulation of floral organ induction and development. Eight full-length cDNAs of HAM (Helianthus annuus MADS) genes have been isolated from sunflower. They encode MADS-box transcription factors expressed in inflorescence tissues. In the frames of the ABCDE model, the HAM proteins were classified according to their structural homology to known MADS-box transcription factors. The HAM45 and HAM59 genes encode the homeotic C function and are involved in the control of the identity of pistil and stamens, while the HAM75 and HAM92 genes determine the A identity of floral and inflorescence meristems and petal identity. The HAM31. HAM2, HAM63, and HAM91 genes encode the B function and are involved in the formation of petals and stamens; and the HAM137 gene encodes the E function. Analysis of the expression of MADS-box genes in sunflower has demonstrated that the structural and functional differences between the ray and tubular flowers in the inflorescence could be a consequence of the lack of HAM59 expression during ray flower initiation.

Evidence for alternative splicing of MADS-box transcripts in developing cotton fibre cells

The MADS-box family of genes encodes transcription factors that have widely ranging roles in diverse aspects of plant development. In this study, four cotton MADS-box cDNA clones of the type II (MIKC) class were isolated, with phylogenetic analysis indicating that the cotton sequences are of the AGAMOUS subclass. The corresponding transcripts were detected in developing cotton fibre cells as well as in whole ovule and flower tissue, with differential expression in stems, leaves and roots. Reverse transcription PCR showed extensive alternative splicing in one of the reactions, and 11 mRNAs of different intron/exon composition and length were characterised. Sequence differences between the transcripts indicated that they could not be derived from the same pre-mRNA and that the sequenced transcript pool was derived from two distinct MADS-box genes. Several of the alternatively spliced transcripts potentially encoded proteins with altered K-domains and/or C-terminal regions and the variant proteins may have altered cellular roles. This work is the first that describes MADS-box gene expression in elongating cotton fibres and adds to a growing body of evidence for the prevalence of alternative splicing in the expression of MADS-box and other genes.

Identification of a protein kinase gene associated with pistillody, homeotic transformation of stamens into pistil-like structures, in alloplasmic wheat

Homeotic transformation of stamens into pistil-like structures (called pistillody) has been reported in cytoplasmic substitution (alloplasmic) lines of bread wheat (Triticum aestivum) having the cytoplasm of a wild relative species, Aegilops crassa. Our previous studies indicated that pistillody is caused by alterations of the class B MADS-box gene expression pattern associated with mitochondrial gene(s) in the Ae. crassa cytoplasm. To elucidate the nuclear gene involved in the cross-talk between pistillody-related mitochondrial gene(s) and nuclear homeotic genes, we performed cDNA subtraction analysis using cDNAs derived from young spikes of a pistillody line and a normal line. As a result, we identified a protein kinase gene, WPPK1 (wheat pistillody-related protein kinase 1), which is upregulated in the young spikes of the pistillody line. RT-PCR analysis indicated that WPPK1 is strongly expressed in pistils and pistil-like stamens in the pistillody line, suggesting that it is involved in the formation of pistil-like stamens as well as pistils. The full-length cDNA sequence for WPPK1 showed high similarity with a flowering plant PVPK-1 protein kinase, and phylogenetic analysis indicated that it is a member of AGC group protein kinases. Furthermore, a phosphorylation assay indicated that it has protein kinase activity. In situ hybridization analysis revealed that WPPK1 is expressed in developing pistils and pistil-like stamens as well as in their primordia. These indicate that in the alloplasmic line, WPPK1 plays a role in formation and development of pistil-like stamens.

Genome-wide analysis of the MADS-box gene family in Populus trichocarpa

Populus trichocarpa (poplar) is distinguished from its herbaceous counterparts Arabidopsis and rice by its woody structure, perennial life cycle, and dioecious, two-whorled flowers. MADS-box genes are known to be involved in many important processes during plant development. Investigation of the poplar genome revealed 105 putative functional MADS-box genes and 12 pseudogenes. These numbers are comparable to those in Arabidopsis. However, poplar has 64 type II MADS-box genes, implying a higher birth rate when compared with Arabidopsis (64 vs.47). In addition to duplications for floral organ identity genes, TM3-like, StMADS11, ANR1 and Bs clades were significantly increased. As indicated by the phylogenetic analysis, there exist at least two MIKC ⁎ MADS-box genes in the poplar genome. In contrast, only 41 putative functional type I genes and 9 pseudogenes were found, suggesting that the poplar type I MADS-box genes have experienced a lower rate in both birth and death. Poplar MADS-box genes were distributed on all linkage groups (LGs), except LG XIX. Like other gene families, poplar MADS-box gene family has expanded through tandem gene duplication and segmental duplication events as demonstrated by two genomic regions where clustered MADS-box genes exhibited high similarities in the MADS-box domains. A survey of poplar EST sequences showed that MADS-box genes were expressed in wood and cambium tissues, which are specific to woody plants. The expression of common MADS-box gene in tree-specific tissues suggests that the novel function combinations of a set of genes similar to those in herbaceous plants may account for the development of woody characteristics in poplar.

Expression of MADS-box genes during the embryonic phase in Arabidopsis

MADS domain factors play important roles as developmental regulators in plants. In Arabidopsis thaliana, MADS domain proteins have been shown to regulate various processes during the vegetative and reproductive phases. Relatively little is known, however, about family members expressed during the embryonic phase and their function. To determine which MADS-box genes are expressed during the embryonic phase in Arabidopsis, a family-wide survey involving gene-specific primers and RT-PCR was conducted. Transcripts corresponding to 64 (out of 109 total) family members could be detected in RNA samples isolated from embryonic culture tissue. Eight MADS-box genes that appear to be expressed at higher levels during the embryonic phase than in seedlings or in inflorescence apices were identified. The spatial pattern of expression in developing seeds was characterized for four MADS-box genes (FLOWERING LOCUS C, FLOWERING LOCUS M, AGAMOUS-LIKE 15, and AGAMOUS-LIKE 18) using reporter constructs encoding translational fusions to GUS. All four are expressed in cells throughout the endosperm and embryo. Finally, to test the hypothesis that AGAMOUS-LIKE15 (AGL15) and AGAMOUS-LIKE18 (AGL18) play essential roles during the embryonic phase, plants carrying T-DNA insertions that disrupt these genes were isolated. No embryo defects were observed in agl15 or agl18 single mutants or in agl15agl18 double mutants. These results indicate that multiple regulatory pathways that involve MADS domain factors are likely to operate in embryonic tissues, and that genetic and/or functional redundancy are likely to be as prevalent as in other phases of the life cycle.

Unravelling MADS-box gene family in Eucalyptus spp.: a starting point to an understanding of their developmental role in trees

MADS-box genes encode a family of transcription factors which control diverse developmental processes in flowering plants ranging from root to flower and fruit development. Members of the MADS-box gene family share a highly conserved sequence of approximately 180 nucleotides that encodes a DNA-binding domain. We used bioinformatics tools to investigate the information generated by the Eucalyptus Expressed Sequence Tag (FORESTs) genome project in order to identify and annotate MADS-box genes. The comparative phylogenetic analysis of the Eucalyptus MADS-box genes with Arabidopsis homologues allowed us to group them into one of the well-known subfamilies. Trends in gene expression of these putative Eucalyptus MADS-box genes were investigated by hierarchical clustering analysis. Among 24 MADS-box genes identified by our analysis, 12 are expressed in vegetative organs. Out of these, five are expressed predominately in wood. Understanding of the molecular mechanisms performed by MADS-box proteins underlying Eucalyptus growth, development and stress reactions would provide important insights into tree development and could reveal means by which tree characteristics could be modified for the improvement of industrial properties.

On the origin of floral morphological novelties

Floral morphological novelties, like homeotic changes of whorl 1 organs, can easily arise by modifying existing regulatory networks. Ectopic expression of B-function MADS-box genes in whorl 1 leads to a replacement of sepals by petals, as is found in the Liliaceae. In cases where leaf-like sepals or even inflated calyces develop, which ultimately envelop the mature fruit as in Physalis, ectopic expression of a vegetative MADS-box gene seems to be responsible. Current knowledge concerning the origin of such morphological novelties is reviewed.

Pistillody is caused by alterations to the class-B MADS-box gene expression pattern in alloplasmic wheats.

Class-B floral homeotic genes are involved in specifying petal and stamen identity during flower development in plant species. Homeotic transformation of stamens into pistil-like structures (called pistillody) has been observed in alloplasmic lines of bread wheat ( Triticum aestivum L.) having the cytoplasm of a wild relative species, Aegilops crassa Boiss. To obtain information about the molecular mechanism underlying pistillody induction, we isolated two PISTILLATA ( PI)-type class-B MADS-box genes, WPI1 ( wheat PI STILLATA # 1) and WPI2, from wheat. Phylogenetic reconstruction indicated that WPI1 is orthologous to OsMADS4 and that WPI2 is probably an ortholog of OsMADS2. Both OsMADS4 and OsMADS2 genes were suggested to be PI orthologs in rice, and the function of OsMADS4 as a class-B gene was proven by the transgenic study. An in situ hybridization study demonstrated that the WPI1 gene is expressed in primordia of lodicules and stamens in developing florets in wheat. In the alloplasmic wheat line exhibiting pistillody, the WPI1 transcripts were not detected in the primordia of pistil-like stamens, whereas WPI1 was expressed in the lodicules. The wheat APETALA3 ( AP3)-type class-B MADS-box gene WAP3 ( wheat AP3) /TaMADS#82 showed an expression pattern similar to that of WPI1. These results suggest that pistillody in alloplasmic wheats is caused by alterations to the expression pattern of class-B MADS-box genes.