Transcriptome analyses at specific plastochrons reveal timing and involvement of phytosulfokine in maize vegetative phase change.

Successive developmental stages of representative early and late juvenile, transition, and adult maize leaves were compared using machine-learning-aided analyses of gene expression patterns to characterize vegetative phase change (VPC), including identification of the timing of this developmental transition in maize. We used t-SNE to organize 32 leaf samples into 9 groups with similar patterns of gene expression. oposSOM yielded clusters of co-expressed genes from key developmental stages.

Auxin Involvement in Ceratopteris Gametophyte Meristem Regeneration.

Growth and development of the Ceratopteris hermaphroditic gametophytes are dependent on cell proliferation in the marginal meristem, which when destroyed will regenerate at a new location on the body margin. We established a laser ablation method to destroy a single initial cell in the meristem. Ablation caused the cessation of cell proliferation accompanied by the disappearance of the expression of an auxin synthesis gene () and a cell proliferation marker gene ().

A Ceratopteris EXCESS MICROSPOROCYTES1 suppresses reproductive transition in the fern vegetative leaves.

Land plant sexual reproduction involves the transition of cells from somatic to reproductive identity during post-embryonic development. In Arabidopsis, the leucine-rich repeat receptor-like kinase EXCESS MICROSPOROCYTES1 (EXS/EMS1) restricts the number of sporogenous cells during the transition from diploid tissue to haploid spore production by promoting the formation of the tapetum cell layer within the anther. Although all land plants studied contain EMS1 genes, its function is unknown beyond a few angiosperms.

Vascular function of the T3/modern clade WUSCHEL-Related HOMEOBOX transcription factor genes predate apical meristem-maintenance function.

Background: Plants have the lifelong ability to generate new organs due to the persistent functioning of stem cells. In seed plants, groups of stem cells are housed in the shoot apical meristem (SAM), root apical meristem (RAM), and vascular cambium (VC). In ferns, a single shoot stem cell, the apical cell, is located in the SAM, whereas each root initiates from a single shoot-derived root initial.

The integration of leaf-derived signals sets the timing of vegetative phase change in maize, a process coordinated by epigenetic remodeling.

After germination, the maize shoot proceeds through a series of developmental stages before flowering. The first transition occurs during the vegetative phase where the shoot matures from the juvenile to the adult phase, called vegetative phase change (VPC). In maize, both phases exhibit easily-scored morphological characteristics, facilitating the elucidation of molecular mechanisms directing the characteristic gene expression patterns and resulting physiological features of each phase.

Jasmonic acid levels decline in advance of the transition to the adult phase in maize.

Leaf-derived signals drive the development of the shoot, eventually leading to flowering. In maize, transcripts of genes that facilitate jasmonic acid (JA) signaling are more abundant in juvenile compared to adult leaf primordia; exogenous application of JA both extends the juvenile phase and delays the decline in miR156 levels. To test the hypothesis that JA promotes juvenility, we measured JA and meJA levels using LC-MS in successive stages of leaf one development and in later leaves at stages leading up to phase change in both normal maize and phase change mutants.

A fern WUSCHEL-RELATED HOMEOBOX gene functions in both gametophyte and sporophyte generations.

Background: Post-embryonic growth of land plants originates from meristems. Genetic networks in meristems maintain the stem cells and direct acquisition of cell fates. WUSCHEL-RELATED HOMEOBOX (WOX) transcription factors involved in meristem networks have only been functionally characterized in two evolutionarily distant taxa, mosses and seed plants.

Characterization of Dialkyldithiophosphates as Slow Hydrogen Sulfide Releasing Chemicals and Their Effect on the Growth of Maize.

Hydrogen sulfide is a key gasotransmitter for plants and has been shown to greatly increase their growth and survival in the presence of environmental stressors. Current methods for slowly releasing hydrogen sulfide use chemicals, such as GYY-4137, but these result in the release of chemicals not found in the environment, and chemicals used may lack structures that can be readily tuned to affect the rate of release of hydrogen sulfide. In this article, we describe the synthesis and slow release of hydrogen sulfide from dialkyldithiophosphates, which are a new set of hydrogen sulfide releasing chemicals that can be used in agriculture.

Improved growth of pea, lettuce, and radish plants using the slow release of hydrogen sulfide from GYY-4137.

Hydrogen sulfide (H2S) is a key gasotransmitter in agriculture and has been reported to increase the growth of plants in the first two weeks and to mitigate the effects of environmental stressors. GYY-4137 is widely used in these studies because it slowly releases H2S, but there is disagreement as to whether it requires enzymes to release H2S. In this article we describe the release of H2S in water without enzymes and that it releases H2S faster in organic solvents than in water or when mixed in topsoil.

A fern AINTEGUMENTA gene mirrors BABY BOOM in promoting apogamy in Ceratopteris richardii.

Asexual reproduction is widespread in land plants, including ferns where 10% of all species are obligate asexuals. In these ferns, apogamous sporophytes are generated directly from gametophytes, bypassing fertilization. In the model fern Ceratopteris richardii, a sexual species, apogamy can be induced by culture on high sugar media.

The Juvenile Phase of Maize Sees Upregulation of Stress-Response Genes and Is Extended by Exogenous Jasmonic Acid.

As maize (Zea mays) plants undergo vegetative phase change from juvenile to adult, they both exhibit heteroblasty, an abrupt change in patterns of leaf morphogenesis, and gain the ability to produce flowers. Both processes are under the control of microRNA156 (miR156), whose levels decline at the end of the juvenile phase. Gain of the ability to flower is conferred by the expression of miR156 targets that encode SQUAMOSA PROMOTER-BINDING transcription factors, which, when derepressed in the adult phase, induce the expression of MADS box transcription factors that promote maturation and flowering.

Transient and stable transformation of Ceratopteris richardii gametophytes.

Background: Ferns, being vascular yet seedless, present unparalleled opportunities to investigate important questions regarding the evolution and development of land plants. Ceratopteris richardii, a diploid, homosporous fern has been advanced as a model fern system; however, the tenuous ability to transform the genome of this fern greatly limited its usefulness as a model organism. Here we report a simple and reliable Agrobacterium-mediated method for generating transient and stable transformants of mature C.

Gene expression associated with apogamy commitment in Ceratopteris richardii.

Apogamy is a phenomenon in which a sporophyte develops asexually, directly from a cell or cells of a gametophyte. It is a phenomenon described mainly in lower plants, but shares certain aspects with apomixis in angiosperms. The genes involved in apogamy commitment in ferns are unknown.

Microarray analysis of vegetative phase change in maize.

Vegetative phase change is the developmental transition from the juvenile phase to the adult phase in which a plant becomes competent for sexual reproduction. The gain of ability to flower is often accompanied by changes in patterns of differentiation in newly forming vegetative organs. In maize, juvenile leaves differ from adult leaves in morphology, anatomy and cell wall composition.

The maize tasselseed4 microRNA controls sex determination and meristem cell fate by targeting Tasselseed6/indeterminate spikelet1.

In maize (Zea mays), sex determination occurs through abortion of female carpels in the tassel and arrest of male stamens in the ear. The Tasselseed6 (Ts6) and tasselseed4 (ts4) mutations permit carpel development in the tassel while increasing meristem branching, showing that sex determination and acquisition of meristem fate share a common pathway. We show that ts4 encodes a mir172 microRNA that targets APETALA2 floral homeotic transcription factors.

Rejuvenation by shoot apex culture recapitulates the developmental increase of methylation at the maize gene Pl-Blotched.

Cytosine methylation provides an attractive epigenetic modification for the global maintenance of phases in plant development; however, there are few known examples of specific genes whose methylation status changes in a developmentally regulated manner. Pl-Blotched, an allele of purple plant1 (pl1), which encodes a myb-like transcription factor that regulates anthocyanin production in maize, is one such gene: certain cytosines at the 3' end of this allele are hypomethylated in seedlings, become hypermethylated in organs formed in the adult phase, and are hypomethylated again in the next generation. We tested whether this developmental pattern of low juvenile cytosine methylation followed by higher methylation in adult tissues could also be observed in plants "rejuvenated" via shoot apex culture.

JOINTLESS suppresses sympodial identity in inflorescence meristems of tomato.

Unlike monopodial plants, in which flowering terminates growth of a shoot, plants exhibiting sympodial shoot architecture maintain the potential for indeterminate growth even after converting to floral development. This vegetative indeterminacy is conferred by a special type of axillary meristem, the sympodial meristem, which exhibits precocious but determinate growth. The reiterative formation of sympodial meristems as the plant grows results in a shoot composed of a series of modules, each consisting of a limited number of vegetative nodes and terminated by a flower or inflorescence.

The wandering carpel mutation of Zea mays (Gramineae) causes misorientation and loss of zygomorphy in flowers and two-seeded kernels.

We have isolated a new mutation, wandering carpel (wcr), which affects polarity of the maize flower, altering its orientation or converting it from zygomorphy to radial symmetry. These changes result in the development of embryos on locations other than the normal, acropetal side of the kernel. More than two carpels can develop into silks.