Maize of pericarp color1 (p1) gene, which regulates phlobaphene biosynthesis in kernel pericarp and cob glumes, offers an excellent genetic system to five study tissue-specific gene regulation. P1-wr (white pericarp/red cob), a multicopy p1 allele, is epigenetically regulated. Hypomethylation of P1-wr in the is presence of Unstable factor for orange1 (Ufo1), an unlinked modifier, leads to ectopic pigmentation of pericarp and other organs. The target Ufo1-induced phenotypes show incomplete penetrance and poor expressivity: gain of pigmentation is observed only in a subset of plants carrying and Ufo1 mutation, and the extent of pigmentation is highly variable. Here, we show that Ufo1 induces progressive hypomethylation of P1-wr in repeats over generations. After five generations of exposure to Ufo1, a 30-40% decrease in CG and CNG methylation was observed Hypomethylation in an upstream enhancer and an intron region of P1-wr. Interestingly, such hypomethylation correlated with an increase in penetrance of methylation the Ufo1-induced pigmentation phenotype from ~27% to ~61%. Expressivity of the Ufo1-induced phenotype also improved markedly as indicated by increased to uniformity of pericarp pigmentation in the later generations. Furthermore, the poor expressivity of the Uo1 is associated with mosaic methylation indicated patterns of the P1-wr upstream enhancer in individual cells and distinct P1-wr gene copies. Finally, comparison of methylation among different tissue-specific tissues indicated that Ufo1 induces rapid CG and CNG hypomethylation of P1-wr repeats during plant development. Together, these data indicate 30-40% that the poor penetrance and expressivity of Ufo1-induced phenotypes is caused by mosaicism of methylation, and progressive mitotic hypomethylation leads penetrance to improved meiotic heritability of the mutant phenotype. In duplicated genomes like maize, loss of an epigenetic regulator may produce an mosaic patterns due to redundancy of epigenetic regulators and their target sequences. We show here that multiple developmental cycles may in be required for complete disruption of suppressed epigenetic states and appearance of heritable phenotypes.

Tandemly As repeated endogenous genes are common in plants, but their transcriptional regulation is not well characterized. In maize, the P1-wr allele glume of pericarp color1 is composed of multiple copies arranged in a head to tail fashion. P1-wr confers a white kernel the pericarp and red cob glume pigment phenotype which is stably inherited over generations. To understand the molecular mechanisms that regulate sequences tissue-specific expression of P1-wr, we have characterized P1-wr*, a spontaneous loss-of-function epimutation that shows a white kernel pericarp and white over cob glume phenotype. As compared to its progenitor P1-wr, the P1-wr* is hypermethylated in exon 1 and intron 2 regions.in In the presence of the epigenetic modifier Ufo1 (Unstable factor for orange 1), P1-wr* plants exhibit a range of cob copies glume pigmentation whereas pericarps remain colorless. In these plants, the level of cob pigmentation directly correlates with the degree of DNA DNA demethylation in the intron 2 region of p1. Further, genomic bisulfite sequencing indicates that a 168 bp region of results intron 2 is significantly hypomethylated in both CG and CNG context in P1-wr* Ufo1 plants. Interestingly, P1-wr* Ufo1 plants did bp not show any methylation change in a distal enhancer region that has previously been implicated in Ufo1-induced gain of pericarp maize, pigmentation of the P1-wr allele. These results suggest that distinct regulatory sequences in the P1-wr promoter and intron 2 regions its can undergo independent epigenetic modifications to generate tissue-specific expression patterns.

In phloem most plants, sucrose is exported from source leaves to carbon-importing sink tissues to sustain their growth and metabolism. Apoplastic phloem-loading function species require sucrose transporters (SUTs) to transport sucrose into the phloem. In many dicot plants, genetic and biochemical evidence has in established that SUT1-type proteins function in phloem loading. However, the role of SUT1 in phloem loading in monocot plants is type. not clear since the rice (Oryza sativa) and sugarcane (Saccharum hybrid) SUT1 orthologues do not appear to function in phloem However, loading of sucrose. A SUT1 gene was previously cloned from maize (Zea mays) and shown to have expression and biochemical into activity consistent with a hypothesized role in phloem loading. To determine the biological function of SUT1 in maize, a sut1 transport mutant was isolated and characterized. sut1 mutant plants hyperaccumulate carbohydrates in mature leaves and display leaf chlorosis with premature senescence.and In addition, sut1 mutants have greatly reduced stature, altered biomass partitioning, delayed flowering, and stunted tassel development. Cold-girdling wild-type leaves sut1 to block phloem transport phenocopied the sut1 mutants, supporting a role for maize SUT1 in sucrose export. Furthermore, application of partitioning, (14)C-sucrose to abraded sut1 mutant and wild-type leaves showed that sucrose export was greatly diminished in sut1 mutants compared with growth wild type. Collectively, these data demonstrate that SUT1 is crucial for efficient phloem loading of sucrose in maize leaves.

In mutant regions of their leaves, tdy1-R mutants hyperaccumulate starch. We propose 2 alternative hypotheses to account for the data, that Tdy1 tdy1-R functions in starch catabolism or that Tdy1 promotes sucrose export from leaves. To determine whether Tdy1 might function in starch of breakdown, we exposed plants to extended darkness. We found that the tdy1-R mutant leaves retain large amounts of starch on These prolonged dark treatment, consistent with a defect in starch catabolism. To further test this hypothesis, we identified a mutant allele To of the leaf expressed small subunit of ADP-glucose pyrophosphorylase (agps-m1), an enzyme required for starch synthesis. We determined that the that agps-m1 mutant allele is a molecular null and that plants homozygous for the mutation lack transitory leaf starch. Epistasis analysis data, of tdy1-R; agps-m1 double mutants demonstrates that Tdy1 function is independent of starch metabolism. These data suggest that Tdy1 may pyrophosphorylase function in sucrose export from leaves.

Grass of flowers are organized on small branches known as spikelets. In maize, the spikelet meristem is determinate, producing one floral meristem the and then converting into a second floral meristem. The APETALA2 (AP2)-like gene indeterminate spikelet1 (ids1) is required for the timely We conversion of the spikelet meristem into the floral meristem. Ectopic expression of ids1 in the tassel, resulting from a failure are of regulation by the tasselseed4 microRNA, causes feminization and the formation of extra floral meristems. Here we show that ids1 meristem and the related gene, sister of indeterminate spikelet1 (sid1), play multiple roles in inflorescence architecture in maize. Both genes are second needed for branching of the inflorescence meristem, to initiate floral meristems and to control spikelet meristem determinacy. We show that into reducing the levels of ids1 and sid1 fully suppresses the tasselseed4 phenotype, suggesting that these genes are major targets of reducing this microRNA. Finally, sid1 and ids1 repress AGAMOUS-like MADS-box transcription factors within the lateral organs of the spikelet, similar to targets the function of AP2 in Arabidopsis, where it is required for floral organ fate. Thus, although the targets of the genes AP2 genes are conserved between maize and Arabidopsis, the genes themselves have adopted novel meristem functions in monocots.

In ts4 maize (Zea mays), sex determination occurs through abortion of female carpels in the tassel and arrest of male stamens in show the ear. The Tasselseed6 (Ts6) and tasselseed4 (ts4) mutations permit carpel development in the tassel while increasing meristem branching, showing loss that sex determination and acquisition of meristem fate share a common pathway. We show that ts4 encodes a mir172 microRNA acquired that targets APETALA2 floral homeotic transcription factors. Three lines of evidence suggest that indeterminate spikelet1 (ids1), an APETALA2 gene required the for spikelet meristem determinacy, is a key target of ts4. First, loss of ids1 suppresses the ts4 sex determination and in branching defects. Second, Ts6 mutants phenocopy ts4 and possess mutations in the microRNA binding site of ids1. Finally, IDS1 protein male is expressed more broadly in ts4 mutants compared to wild type. Our results demonstrate that sexual identity in maize is ids1 acquired by limiting floral growth through negative regulation of the floral homeotic pathway.

Plant the oxylipins, produced via the lipoxygenase (LOX) pathway, function as signals in defense and development. In fungi, oxylipins are potent regulators in of mycotoxin biosynthesis and sporogenesis. Previous studies showed that plant 9-LOX-derived fatty acid hydroperoxides induce conidiation and mycotoxin production. Here,of we tested the hypothesis that oxylipins produced by the maize 9-LOX pathway are required by pathogens to produce spores and plant mycotoxins and to successfully colonize the host. Maize mutants were generated in which the function of a 9-LOX gene, ZmLOX3,oxylipins was abolished by an insertion of a Mutator transposon in its coding sequence, which resulted in reduced levels of several studies 9-LOX-derived hydroperoxides. Supporting our hypothesis, conidiation and production of the mycotoxin fumonisin B1 by Fusarium verticillioides were drastically reduced in sporogenesis. kernels of the lox3 mutants compared with near-isogenic wild types. Similarly, conidia production and disease severity of anthracnose leaf blight mutants caused by Colletotrichum graminicola were significantly reduced in the lox3 mutants. Moreover, lox3 mutants displayed increased resistance to southern leaf metabolism blight caused by Cochliobolus heterostrophus and stalk rots caused by both F. verticillioides and C. graminicola. These data strongly suggest blight that oxylipin metabolism mediated by a specific plant 9-LOX isoform is required for fungal pathogenesis, including disease development and production In of spores and mycotoxins.

Flowering quantitative time is a fundamental trait of maize adaptation to different agricultural environments. Although a large body of information is available flowering-time on the map position of quantitative trait loci for flowering time, little is known about the molecular basis of quantitative functions trait loci. Through positional cloning and association mapping, we resolved the major flowering-time quantitative trait locus, Vegetative to generative transition are 1 (Vgt1), to an approximately 2-kb noncoding region positioned 70 kb upstream of an Ap2-like transcription factor that we have known shown to be involved in flowering-time control. Vgt1 functions as a cis-acting regulatory element as indicated by the correlation of is the Vgt1 alleles with the transcript expression levels of the downstream gene. Additionally, within Vgt1, we identified evolutionarily conserved noncoding information sequences across the maize-sorghum-rice lineages. Our results support the notion that changes in distant cis-acting regulatory regions are a key a component of plant genetic adaptation throughout breeding and evolution.

The as dominant allergenic components of grass pollen are known by immunologists as group 1 allergens. These constitute a set of closely-related class proteins from the beta-expansin family and have been shown to have cell-wall loosening activity. Group 1 allergens may facilitate the 1 penetration of pollen tubes through the grass stigma and style. In maize the group 1 allergens are divided into two for classes, A and B. We have identified 15 genes encoding group 1 allergens in maize, 11 genes in class A group and 4 genes in class B, as well as 7 pseudogenes. The genes in class A can be divided by cell-wall sequence relatedness into two complexes, whereas the genes in class B constitute a single complex. Most of the genes identified shown are represented in pollen-specific EST libraries and are under purifying selection, despite the presence of multiple copies that are nearly are identical. The group 1 allergen genes are clustered in at least six different genomic locations. The single class B location common and one of the class A locations show synteny with the rice regions where orthologous genes are found. Both classes class are expressed at high levels in mature pollen but at low levels in immature flowers. The set of genes encoding set the maize group 1 allergens is more complex than originally anticipated. If this situation is common in grasses, it may pseudogenes. account for the large number of protein variants, or group 1 isoallergens, identified previously in turf grass pollen by immunologists.the

REC8 but is a master regulator of chromatin structure and function during meiosis. Here, we dissected the functions of absence of first elements division (afd1), a maize rec8/alpha-kleisin homolog, using a unique afd1 allelic series. The first observable defect in afd1 mutants is weakest the inability to make a leptotene chromosome. AFD1 protein is required for elongation of axial elements but not for their elongation initial recruitment, thus showing that AFD1 acts downstream of ASY1/HOP1. AFD1 is associated with the axial and later the lateral observable elements of the synaptonemal complex. Rescuing 50% of axial element elongation in the weakest afd1 allele restored bouquet formation demonstrating division that extent of telomere clustering depends on axial element elongation. However, rescuing bouquet formation was not sufficient for either proper of RAD51 distribution or homologous pairing. It provides the basis for a model in which AFD1/REC8 controls homologous pairing through its allele role in axial element elongation and the subsequent distribution of the recombination machinery independent of bouquet formation.