POC Conf. Call 10-15-13

POC meeting, Skype Conference Call; Date: Tuesday Oct 15th, 2013 10:30am PST/1:30pm EST

In attendance:

Absent:

vascular leaf development stage and child terms

• Continued from POC_Conf._Call_9-24-13, POC_Conf._Call_10-1-13

Proposed new term and definition:

• vascular leaf development stage (new PO:0025570): A leaf development stage (PO:0001050) which begins with the onset of the vascular leaf initiation stage (PO:0001051) and ends with the termination of the vascular leaf senescence stage (PO:0001054).
  • No comment currently

vascular leaf initiation stage (PO:0007040) and child terms:

• vascular leaf initiation stage (PO:0007040):

• Revised def'n: A vascular leaf development stage (PO:0025570) which begins with the onset of the vascular leaf anlagen formation stage (PO:0001003) and ends with the termination of the vascular leaf primordium polarity determination stage (PO:0001052).

• Revised Comment: Localized cell divisions in the peripheral zone (PO:0000225) transition from anticlinal to periclinal divisions.

vascular leaf anlagen formation stage (PO:0001003)

• Revised name and definition: vascular leaf anlagen formation stage (PO:0001003): A vascular leaf initiation stage (PO:0007040) during which the vascular leaf founder cells (PO:0025592) of the shoot apical meristem (PO:0020148) form a vascular leaf anlagen (PO:0025431).

Revised comment: The initial stage of leaf development when cells in the shoot apical meristem (PO:0020148) are already determined to form a vascular leaf primordium (PO:0000017), but the primordium is not yet morphologically distinguishable.

Added revised synonym (exact): vascular leaf founder cell formation stage

New terms for founder cells:

• phyllome founder cell (new PO:0025586): A plant cell (PO:0009002) that is part of the phyllome anlagen (PO:0025430).

Comment: As a group, the phyllome founder cells encompass several layers of the shoot apical meristem (PO:0020148) and form a phyllome anlagen (PO:0025430). Founder cells do not function as stem cells but rather have a determinate fate and can be defined by histological, clonal and molecular criteria.

• vascular leaf founder cell (new PO:0025592): A phyllome founder cell (PO:0025586) that is part of a vascular leaf anlagen (PO:0025431).

Comment: As a group, the vascular leaf founder cells encompass several layers of the shoot apical meristem (PO:0020148) and form a vascular leaf anlagen (PO:0025431). Founder cells do not function as stem cells but rather have a determinate fate and can be defined by histological, clonal and molecular criteria.

LC: I think we could improve on these definitions

• Definition from Nature Review: Tsiantis1 & Hay, 2003:

LEAF FOUNDER CELLS: A group of cells that encompasses several layers of the shoot apical meristem and from which a leaf primordium is derived. Founder cells do not function as stem cells but rather have a determinate fate and can be defined by histological, clonal and molecular criteria.

• Question about making the participates_in relation to vascular leaf anlagen formation stage: should it be the vascular leaf anlagen or the vascular leaf founder cell?

references for anlagen and founder cells

"The development of a leaf begins with a regional shift in the polarity and rate of cell division and expansion within a group of leaf founder cells on the flank of shoot apical meristem." Smith and Hake 1992

See image: founder-cell population (FC) that will give rise to the next leaf primordium

Goh et al, 2012 Development

PO-dev Feb.06

vascular leaf primordium formation stage (PO:0001019)

• Revised name and def'n: vascular leaf primordium formation stage (PO:0001019): A vascular leaf initiation stage (PO:0001051) during which a vascular leaf primordium (PO:0000017) forms in the peripheral zone (PO:0000225) of the vegetative shoot apical meristem (PO:0020148).

Revised comment: The vascular leaf primordium (PO:0000017) develops from the vascular leaf anlagen (PO:002543).

vascular leaf primordium polarity determination stage (new PO:0025572)

* vascular leaf primordium polarity determination stage (PO:0025572): A vascular leaf initiation stage (PO:0001051) during which the vascular leaf primordium (PO:0004725) develops an adaxial side (PO:0004726) and an abaxial side (PO:0004725).

Comment: The vascular leaf primordium adaxial side (PO:0004726) is the closest side to the meristem. This stage leads to the development of a bifacial vascular leaf.

decided to use "proximal" rather than 'closer to'

This term refers to the following two terms (children of phyllome primordium (PO:0025128); both have also been revised:

• New name and def'n: vascular leaf primordium adaxial side (PO:0004726): "A portion of vascular leaf primordium (PO:0000017) that faces the shoot apical meristem (PO:0020148) and develops into the adaxial (upper) side of the leaf lamina (PO:0020039).

• New name and def'n: vascular leaf primordium abaxial side (PO:0004725): A portion of vascular leaf primordium (PO:0000017) that faces away from the shoot apical meristem (PO:0020148) and develops into the abaxial (lower) side of the leaf lamina (PO:0020039).

Comments: The vascular leaves (PO:0009025) of some plants may not have an obvious adaxial or abaxial side such as the leaves of many xerophytic (arid-adapted) species. The adaxial and abaxial side may appear considerably more rounded and this could be due to early activity of the vascular leaf adaxial meristem (PO:0025401) and/or leaf abaxial meristem (PO:0025401).

vascular leaf differentiation stage (new PO:0025574)

This term was proposed during last POC conference call to emphasize the importance of cell and tissue differentiation. vascular leaf differentiation stage (new PO:0025574): A vascular leaf development stage (PO:0025570) that begins with the formation of cambial initial cells (PO:0000295) and epidermal initial cells (PO:0000349) and ends with the formation of the leaf epidermis (PO:0006016) and the leaf vascular system (PO:0000036).

Proposed comment: tba

Need a term procambium initial cell and

Gonzalez et al 2012, Trends in Plant Science

vascular leaf expansion stage PO:0001052

old name and def'n: 2 leaf expansion stage (PO:0001052): Stage of leaf development which begins when cell differentiation and cell expansion occurs and finishes when the leaf reaches its full size.

Proposed revised name and def'n vascular leaf expansion stage (PO:0001052): A vascular leaf development stage (PO:0025570) during which vascular leaf size increases primarily through cell expansion.

Proposed comment: During this stage leaf shaping (GO:0010358) occurs which is defined as the developmental process that pertains to the organization of a leaf in three-dimensional space once the structure has initially formed.

• Note: The majority of cell division occurs early in leaf development and cell expansion is the major agent of leaf expansion link or see above image.

From Esau 1965: It appears that leaf differentiation occurs during the intercallary growth of the leaf. The difference between palisade and spongy mesophyll/cells is a matter of individual growth or elongation.

vascular leaf post-expansion stage (PO:0001053):

old name and def'n: 3 leaf fully expanded stage (PO:0001053): Stage of leaf development when leaf is fully expanded.

Proposed new Name and def'n: vascular leaf post-expansion stage: A vascular leaf development stage (PO:0025570) that begins when the vascular leaf (PO:0009025) is fully expanded and ends with the onset of the vascular leaf senescence stage (PO:0001054).

from 9-10-13: Perhaps change term to "vascular leaf mature stage", or maybe keep the "leaf fully expanded stage"???. Examples of leaves with indeterminate growth, ferns, viney leaves, some Mahogany plants, but they are the exceptions. Could add as a comment (get names from DWS).

vascular leaf senescence stage (PO:0001054)

• vascular leaf senescence stage (PO:0001054): A vascular leaf development stage (PO:0025570) that begins with the formation of a abscission zone at the base of a vascular leaf (PO:0009025) and ends with leaf separation and death.

Would omit formation of a abscission zone. Perhaps say ends with death of vascular leaf. Need to add the references to the GO terms.

Need to look at this more- abscission zone (PO:0000146) starts in the petioles (are part of the leaf), starts with cell senescence, should refer to 'point of attachment'. Don't need to specify where the abscission zone forms. Note all leaves abscise, end with death of the vascular leaf

Need to review leaf senescence- see plant cell resource

• Links to Relevant References- vascular leaf development
  • Genetic Control of Leaf Development- Plant Cell teaching tools
  • Uchida et al (2010) Coordination of leaf development via regulation of KNOX1 genes. Journal of Plant Research 123: 7–14
  • Comparative plant development: the time of the leaf? Tsiantis & Hay, 2003 Nature Reviews Genetics
  • Li, Brutnell et al (2010) The developmental dynamics of the maize leaf transcriptome. Nat Genet 42: 1060–1067
  • Leaf adaxial–abaxial polarity specification and lamina outgrowth: evolution and development, Plant and Cell Physiology, 2012
  • Gleissberg 2002
  • FERNS: The evolution, morphology, and development of fern leaves, Vasco et al 2013
  • Independent recruitment of a conserved developmental mechanism during leaf evolution
  • Gonzalez et al, Trends in Plant Science 2012

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