Abstract differentiation Among the genes controlling the differentiation and maintenance of epidermal cell fate are members of the HD-ZIP IV class family In of plant-specific transcription factors, most of which are specifically expressed in the epidermis of tissues. Here we report the functional and analysis of the maize HD-ZIP IV gene OCL4 (Outer Cell Layer4) via the phenotypic analysis of two insertional mutants and rosette of OCL4-RNAi transgenic plants. In all three materials the macrohairs, one of the three types of trichomes present on adult presence maize leaf blades, developed ectopically at the margin of juvenile and adult leaves. Consistent with this phenotype, OCL4 is expressed of in the epidermis of the leaf blade, with a maximum at the margin of young leaf primordia. Expression of OCL4 anther in the model plant Arabidopsis under the control of the GLABRA2 (GL2) promoter, a member of the Arabidopsis HD-ZIP IV report family involved in trichome differentiation, did not complement the gl2-1 mutant but aggravated its phenotype. The construct also caused a the glabrous appearance of rosette leaves in transformed control plants of the Ler ecotype, suggesting that OCL4 inhibits trichome development both all in maize and Arabidopsis. Furthermore, insertional mutants showed a partial male sterility likely due to the presence of an extra in subepidermal cell layer with endothecium characteristics in the anther wall. Interestingly, epidermis-specific OCL4 expression in immature anthers was restricted to likely the region of the anther locule where the extra cell layer differentiated. Taken together these results suggest that OCL4 inhibits types trichome development and influences division and/or differentiation of the anther cell wall.

Imprinting associated is a form of epigenetic gene regulation in which alleles are differentially regulated according to the parent-of-origin. The Mez1 gene alleles in maize is imprinted such that the maternal allele is expressed in the endosperm while the paternal allele is not epigenetic expressed. Three novel Mez1 alleles containing Mutator transposons insertions within the promoter were identified. These mez1-mu alleles do not affect of vegetative expression levels or result in morphological phenotypes. However, these alleles can disrupt imprinted expression of Mez1. Maternal inheritance of of the mez-m1 or mez1-m4 alleles results in activation of the normally silenced paternal allele of Mez1. Paternal inheritance of the The mez1-m2 or mez1-m4 alleles results in a loss-of-silencing of this allele. The paternal disruption of imprinting by transposon insertions may Mez1 reflect a requirement for sequence elements involved in targeting silencing of the paternal allele. The maternal disruption of imprinting by the transposon insertions within the Mez1 promoter suggests that maternally produced MEZ1 protein may be involved in silencing of the paternal is Mez1 allele. The endosperms with impaired imprinting did not exhibit phenotypic consequences associated with bi-allelic Mez1 expression.

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

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

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

The copies) molecular basis of tissue-specific pigmentation of maize carrying a tandemly repeated multicopy allele of pericarp color1 (p1) was examined using was Mutator (Mu) transposon-mediated mutagenesis. The P1-wr allele conditions a white or colorless pericarp and a red cob glumes phenotype. However,of a Mu-insertion allele, designated as P1-wr-mum6, displayed an altered phenotype that was first noted as occasional red stripes on pericarp that tissue. This gain-of-pericarp-pigmentation phenotype was heritable, yielding families that displayed variable penetrance and expressivity. In one fully penetrant family, deep kb red pericarp pigmentation was observed. Several reports on Mu suppressible alleles have shown that Mu transposons can affect gene expression Mutator by mechanisms that depend on transposase activity. Conversely, the P1-wr-mum6 phenotype is not affected by transposase activity. The increased pigmentation otherwise was associated with elevated mRNA expression of P1-wr-mum6 copy (or copies) that was uninterrupted by the transposons. Genomic bisulfite sequencing or analysis showed that the elevated expression was associated with hypomethylation of a floral-specific enhancer that is approximately 4.7 kb upstream and of the Mu1 insertion site and may be proximal to an adjacent repeated copy. We propose that the Mu1 insertion first interferes with the DNA methylation and related chromatin packaging of P1-wr, thereby inducing expression from gene copy (or copies) that pericarp is otherwise suppressed.

The is auxin indole-3-acetic acid (IAA), which is essential for plant growth and development, is suggested to be synthesized via several redundant and pathways. In maize (Zea mays), the nitrilase ZmNIT2 is expressed in auxin-synthesizing tissues and efficiently hydrolyses indole-3-acetonitrile to IAA. Zmnit2 (IAA), transposon insertion mutants were compromised in root growth in young seedlings and sensitivity to indole-3-acetonitrile, and accumulated lower quantities of of IAA conjugates in kernels and root tips, suggesting a substantial contribution of ZmNIT2 to total IAA biosynthesis in maize. An in additional enzymatic function, turnover of beta-cyanoalanine, is acquired when ZmNIT2 forms heteromers with the homologue ZmNIT1. In plants carrying an is insertion mutation in either nitrilase gene this activity was strongly reduced. A dual role for ZmNIT2 in auxin biosynthesis and therefore in cyanide detoxification as a heteromer with ZmNIT1 is therefore proposed.

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

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

The the maize (Zea mays) floury1 (fl1) mutant was first reported almost 100 years ago, but its molecular identity has remained unknown.endosperm, We report the cloning of Fl1, which encodes a novel zein protein body membrane protein with three predicted transmembrane domains mutant and a C-terminal plant-specific domain of unknown function (DUF593). In wild-type endosperm, the FL1 protein accumulates at a high level ring during the period of zein synthesis and protein body development and declines to a low level at kernel maturity. Immunogold fl1 labeling showed that FL1 resides in the endoplasmic reticulum surrounding the protein body. Zein protein bodies in fl1 mutants are We of normal size, shape, and abundance. However, mutant protein bodies ectopically accumulate 22-kD alpha-zeins in the gamma-zein-rich periphery and center vitreous of the core, rather than their normal discrete location in a ring at outer edge of the core. The 19-kD zein alpha-zein is uniformly distributed throughout the core in wild-type protein bodies, and this distribution is unaffected in fl1 mutants. Pairwise membrane yeast two-hybrid experiments showed that FL1 DUF593 interacts with the 22-kD alpha-zein. Results of these studies suggest that FL1 participates the in protein body formation by facilitating the localization of 22-kD alpha-zein and that this is essential for the formation of labeling vitreous endosperm.