Seed mucilage in temperate grassland species is unrelated to moisture requirements.

Myxospermy, the release of seed mucilage upon hydration, plays multiple roles in seed biology. Here, we explore whether seed mucilage occurs in a suite of temperate grassland species to test if the prevalence of species producing seed mucilage is associated with habitat type or seed characteristics. Seventy plant species found in wet or dry North American temperate grasslands were tested for the presence of seed mucilage through microscopic examination of seeds imbibed with histochemical stain for mucilage.

Overlapping Localization of MAP65-2, -6, and -7 in Arabidopsis Hypocotyl Cells.

Microtubules are essential components of eukaryotic cells. Myriad proteins associate with microtubules to facilitate the organization and operation of microtubule arrays. Various M icrotubule A ssociated P roteins (MAPs) assist the assembly and function of mitotic spindles and interphase arrays.

Stomatal pore width and area measurements in .

Stomatal pores are adjustable microscopic holes on the surface of photosynthetic tissues that help regulate multiple aspects of plant physiology. Stomatal pores facilitate gas exchange necessary for photosynthesis, water transport, and temperature regulation. Pore size is influenced by many intertwined environmental, molecular, cellular, and physiological cues.

Appearance of microtubules at the cytokinesis to interphase transition in Arabidopsis thaliana.

Microtubule arrays drastically reorganize during the cell cycle to facilitate specific events. Many cells contain a centrosome that dictates the assembly and organization of microtubule arrays. However, plant cells and many others do not contain centrosomes or discrete microtubule organizing centers.

Hornwort Stomata: Architecture and Fate Shared with 400-Million-Year-Old Fossil Plants without Leaves.

As one of the earliest plant groups to evolve stomata, hornworts are key to understanding the origin and function of stomata. Hornwort stomata are large and scattered on sporangia that grow from their bases and release spores at their tips. We present data from development and immunocytochemistry that identify a role for hornwort stomata that is correlated with sporangial and spore maturation.

The FOUR LIPS and MYB88 transcription factor genes are widely expressed in Arabidopsis thaliana during development.

Premise Of The Study: The FOUR LIPS (FLP) and MYB88 transcription factors, which are closely related in structure and function, control the development of stomata, as well as entry into megasporogenesis in Arabidopsis thaliana. However, other locations where these transcription factors are expressed are poorly described. Documenting additional locations where these genes are expressed might define new functions for these genes.

The Arabidopsis leucine-rich repeat receptor-like kinase MUSTACHES enforces stomatal bilateral symmetry in Arabidopsis.

Stomata display a mirror-like symmetry that is adaptive for shoot/atmosphere gas exchange. This symmetry includes the facing guard cells around a lens-shaped and bilaterally symmetric pore, as well as radially arranged microtubule arrays that primarily originate at the pore and then grow outwards. Mutations in MUSTACHES (MUS), which encodes a leucine-rich repeat receptor-like kinase, disrupt this symmetry, resulting in defects ranging from skewed pores and abnormally focused and depolarized radial microtubule arrays, to paired guard cells that face away from each other, or a severe loss of stomatal shape.

Arabidopsis guard cell integrity involves the epigenetic stabilization of the FLP and FAMA transcription factor genes.

Arabidopsis guard cell (GC) fate is conferred via a transient pulse of expression of FAMA that encodes a bHLH transcription factor. Stomata often function for years, suggesting that the FAMA expression window stabilizes long-term GC identity or that additional factors operate. Transgenic lines harboring a copy of a FAMA transgene were found to induce the fate resetting of mature GCs to that of lineage-specific stem cells causing new stomata to arise within shells of the old, a Stoma-in-Stoma (SIS) phenotype.

Deep functional redundancy between FAMA and FOUR LIPS in stomatal development.

Functional redundancy arises between gene paralogs as well as non-homologous genes that play a common role at a shared node. The bHLH transcription factor FAMA, along with the paralogous MYB genes, FOUR LIPS (FLP) and MYB88 all ensure that Arabidopsis stomata contain just two guard cells (GCs) by enforcing a single symmetric precursor cell division before stomatal maturity. Consistent with this function, FLP and FAMA exhibit the same expression pattern in which both translational GFP fusions emit fluorescence just before and after symmetric division; however, FAMA but not FLP is required to confer GC fate.

Progressive transverse microtubule array organization in hormone-induced Arabidopsis hypocotyl cells.

The acentriolar cortical microtubule arrays in dark-grown hypocotyl cells organize into a transverse coaligned pattern that is critical for axial plant growth. In light-grown Arabidopsis thaliana seedlings, the cortical array on the outer (periclinal) cell face creates a variety of array patterns with a significant bias (>3:1) for microtubules polymerizing edge-ward and into the side (anticlinal) faces of the cell. To study the mechanisms required for creating the transverse coalignment, we developed a dual-hormone protocol that synchronously induces ∼80% of the light-grown hypocotyl cells to form transverse arrays over a 2-h period.

MAP65-1 and MAP65-2 promote cell proliferation and axial growth in Arabidopsis roots.

We investigated the role of the Arabidopsis microtubule associated proteins 65-1 and 65-2 (MAP65-1 and MAP65-2) in the control of axial root growth. Transgenic plants expressing fluorescent fusion proteins from native promoters indicated exactly overlapping accumulation of MAP65-1 and MAP65-2 in the root tip and elongation zone. Nearly identical protein accumulation patterns were observed when MAP65-1 and MAP65-2 were expressed behind a constitutive CaMV 35S promoter, suggesting a level of post-transcriptional control that restricts these proteins to rapidly growing portions of the root.

Polar development of preprophase bands and cell plates in the Arabidopsis leaf epidermis.

Preprophase bands are belts of cortical microtubules that appear at the end of interphase and predict where cell plates will fuse with parental walls during division. Phragmoplasts are microtubule-rich arrays that orchestrate the growth and guidance of cell plates during cytokinesis. Descriptions of the development of these arrays often assume non-polar formation, with preprophase bands developing more or less simultaneously around the cell circumference.

Microtubule-associated proteins MAP65-1 and MAP65-2 positively regulate axial cell growth in etiolated Arabidopsis hypocotyls.

The Arabidopsis thaliana MAP65-1 and MAP65-2 genes are members of the larger eukaryotic MAP65/ASE1/PRC gene family of microtubule-associated proteins. We created fluorescent protein fusions driven by native promoters that colocalized MAP65-1 and MAP65-2 to a subset of interphase microtubule bundles in all epidermal hypocotyl cells. MAP65-1 and MAP65-2 labeling was highly dynamic within microtubule bundles, showing episodes of linear extension and retraction coincident with microtubule growth and shortening.

Regulation of cell proliferation in the stomatal lineage by the Arabidopsis MYB FOUR LIPS via direct targeting of core cell cycle genes.

Stomata, which are epidermal pores surrounded by two guard cells, develop from a specialized stem cell lineage and function in shoot gas exchange. The Arabidopsis thaliana FOUR LIPS (FLP) and MYB88 genes encode closely related and atypical two-MYB-repeat proteins, which when mutated result in excess divisions and abnormal groups of stomata in contact. Consistent with a role in transcription, we show here that FLP and MYB88 are nuclear proteins with DNA binding preferences distinct from other known MYBs.

TOO MANY MOUTHS promotes cell fate progression in stomatal development of Arabidopsis stems.

Mutations in TOO MANY MOUTHS (TMM), which encodes a receptor-like protein, cause stomatal patterning defects in Arabidopsis leaves but eliminate stomatal formation in stems. Stomatal development in wild-type and tmm stems was analyzed to define TMM function. Epidermal cells in young tmm stems underwent many asymmetric divisions characteristic of entry into the stomatal pathway.

Microtubule arrays and Arabidopsis stomatal development.

Microtubule arrays in living cells were analysed during Arabidopsis stomatal development in order to more closely define stages in the pathway and contexts where intercellular signalling might operate. Arabidopsis stomata are patterned iteratively via the orientation of an asymmetric division in a cell located next to an existing stoma. It was found that preprophase bands of microtubules (PPBs) were correctly placed away from stomata and from two types of precursor cells.