Summary of Changes to PO May 2011

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General changes

Namespace change: Plant Anatomical Entity

The former plant structure branch of the PO was renamed from Plant Structure Ontology (PSO) to Plant Anatomical Ontology (PAO). The namespace for all anatomical entities is now plant_anatomy, instead of plant_structure. The default namespace for the PO remains plant_ontology, and all PO term ID's will continue to begin with "PO:"

This change reflects the new root term plant anatomical entity (PO:0025131), which was added during the January 2011 release. It also better reflects the content of this branch of the PO, which includes not only plant structures (PO:0009011), but also plant anatomical spaces (PO:0025117) and portions of plant substance (PO:0025161).

Translations

New subsets for Spanish and Japanese synonyms were added to the PO, with the scope exact synonym. All plant anatomy terms now have Spanish synonyms, and most have Japanese synonyms. Spanish synoyms will be incorporated into the live version of the PO, but because of issues with displaying special characters, the Japanese synonyms may be available through a separate file.

Changes to the top level of the PAO

Partonomy of plant structures no longer rooted in whole plant

We removed the part_of relationships to whole plant from all of the other descendents of plant structure, such as plant cell, plant organ and portion of plant tissue. Because plant structure is defined as "An anatomical structure that is or was part of a plant, or was derived from a part of a plant," all children of plant structure can be part of a plant, a former part of a plant (e.g., a piece of wood or a cut flower), or derived from a part of a plant (e.g., and in vitro plant structure). There are many instances of plant structures such as cells, tissue, and organs that are not part of a whole plant, so it is inaccurate to specify the part_of relation between those structures and whole plant. This is particularly true in contemporary plant science, where so many plant structures are grown in plant culture.

New upper-level categories

collective organ part structure (PO:0025269)

Definition: A plant structure composed of two or more cardinal organ parts from adjacent organs and any associated portions of plant tissue.

Comment: A collective organ part structure is composed of parts of multiple organs, but no complete organs. The organ parts are often of the same type (e.g., petioles, carpel walls), but may be of different types. Includes plant structures like a septum that consists of the walls of two fused carpels or a pseudostem that consist of multiple, overlapping leaf sheaths. Unlike a collective plant structure, a collective organ part structure does not contain any complete organs.

This term was need to describe structures that would not fit in any other category.

For now, it only has three children: fruit operculum (PO:0025298), pseudostem (PO:0025248), and septum (PO:0000030).

rhizoid (PO:0030078)

Definition: A plant structure that is a uniseriate filament with positive geotropism that grows from an epidermis or protonema.

Comment: May be unicellular or multicellular. Serves to anchor the plant to the substrate, and may function in nutrient and water uptake. Usually lacks chlorophyll. Includes epidermal rhizoids that grow from the epidermis of bryophytes and pteridophytes in the gametophytic phase or from the stems of some monocots, and protonemal rhizoids that branch from a protonema.

Like trichomes, rhizoids can be either uni- or multi-cellular, which prevents us from defining them as either a plant cell or a portion of plant tissue, so we created a separate upper-level term for rhizoids.

Many types of rhizoids grow from an epidermis, and could be classified trichomes, however, making rhizoid a child of trichome would prevent us from including protonemal rhizoids in the same category (because unlike epidermal rhizoids and trichomes, they do not develop from a type of epidermal initial).

Changes in 'in vitro plant structure' (PO:0000004), and its children

We agreed (4-12-11 POC) to make the in vitro structures children of their respective plant structure parents (cell, tissue and embryo) and keep "in vitro plant structure" and use a textual definition and assert dual parentage to it. This was after consultation with PATO, OBI, and GO; CM. Both of the parentage relations had to be asserted in this case because (fill in reason).

This is how it looked before:

This is how it looks now: Make better image with the rest of the terms

Changes in embryo plant structure and its children

Also at the third level, a new term embryonic plant structure was added, as a direct child of plant structure. Only structures that occur exclusively in embryos are defined as children of embryonic plant structure (e.g., coleoptile, suspensor or embryo proper), while plant structures that may be part of either an embryo or an adult plant structure (e.g., parenchyma) are not classified as embryonic plant structures. Embryonic plant structure is defined logically using intersection_of relations, as the intersection of is_a plant structure and part_of embryo. Thus, embryo vascular system, which is_a vascular system and part_of embryo, is automatically inferred to be an embryonic plant structure (see below under “Cross-products in the ontology using the intersection_of relation”). Likewise, embryonic plant cell is defined as the intersection of is_a plant cell and part_of embryo, and portion of embryonic plant tissue is defined as the intersection of is_a portion of plant tissue and part_of embryo.

New relations

participates_in

Unlike other relations in the PO, participates_in provides a link between an independent occurant in the PSO (a plant anatomical entity) and a continuant in the PGDSO (a growth and developmental stage). Participates_in is a specific case of the more general inheres_in relation, as occurrants (i.e., things) generally inhere in continuants (i.e., processes) (Grennon et al., 2004). The addition of the participates_in relation allowed us to remove whole plant structures such as gametophyte, sporophyte, and seedling from the PSO, and describe them as whole plants that participate in their respective life-cycle phases. It also provides a way of more clearly defining structures that occur only in the gametophytic or sporophytic phase, such as, archegonium participates_in gametophytic phase or vascular tissue participates_in sporophytic phase. This allows for comparisons of analogous structures in the gametophytic phase or sporophytic phase that would not normally be grouped together based on homology (such as vascular versus non-vascular leaves, fig. x – still under construction).

adjacent_to

Used when one plant structure (the child) is in permanent contact with another plant structure (the parent).

intersection_of (cross-product definitions)

Cross-product definitions using intersection_of relations are particularly useful when there is a need to organize concepts under multiple ontology classes. For example, as described above, portion of embryonic plant tissue is defined as the intersection_of: is_a portion of plant tissue and intersection_of: part_of embryo. Therefore, we are able to classify, for example, embryo epidermis as a sub-class of epidermis (which is a subclass of portion of plant tissue), yet also infer that embryo epidermis is a subclass of embryonic plant structure. Users who wish to examine all types of plant tissue will still find embryo epidermis under portion of plant tissue, while users who wish to examine all types of embryonic plant structures will also find embryo epidermis under portion of embryonic plant tissue, and therefore under embryonic plant structure.

portions of phyllome epidermis

Added stamen epidermis intersection_of is_a epidermis, intersection_of part_of stamen. Did the same thing for other phyllome epidermises (except the various leaf abaxial and leaf adaxial stomatal epidermises). This allows stomatal complexes and prickles to be inferred is_a children of their respective portions of epidermal tissue, without creating dual parentage.

User requests

Terms requested by TAIR

dispersed meristematic cell

We add leaf procambial cell, in response to the request for "dispersed meristematic cell". Dispersed meristematic cell and DMC were added as exact synonyms.

To accomodate this request, the following changes were made to the PO hierarchy:

meristematic cell (PO:0004010)

-[is_a] procambial cell (PO:0025258) (new)

- -[is_a] leaf procambial cell (PO:0000063) (new)

procambium (PO:0006074)

-[is_a] leaf procambium (PO:0025259) (new)

- -[part_of] leaf procambial cell (PO:0000063) (new)

ovary septum vs. carpel septum

There was a request for a new term 'ovary septum.' but after a long discussion on SF, the conclusion seems to be that ovary septum should be a synonym of carpel septum.

Current definition of carpel septum (PO:0005009): A thin partition or membrane that divides multilocular ovary. Often found in species with syncarpous (multiple carpels fused) pistil. [source: GR:cwt, GR:pj]

Suggest placing the second sentence in a comment and removing the word often.

Suggested definition: septum that divides a multilocular ovary. Comment: Found in species with syncarpous gynoecia (fused carpels). Synonym: ovary septum

Current def'n: septum (PO:0000030): A thin partition or membrane that divides a cavity or a mass of tissue, e.g., in anther, ovary or fruit. [source: APWeb:Glossary], is_a portion of plant tissue.

Suggest that septum should be a cardinal organ part, rather than a portion of plant tissue.

Proposed def'n: A cardinal organ part that forms a partition that divides a cavity formed by the fusion several plant structures such as anthers or ovaries.

New proposed def'n:

A plant structure composed of two or more layers of various tissues that form a partition that divides a cavity formed by the fusion of two or more organs.

-add comments: like an orange in cross-section, white part= "albedo",

-Look for an image to illustrate this, look on plantsystematic.org, add link to image

Comment: A septum is formed by the fusion of the walls of two adjacent organ parts (ovary walls or anther walls).

Question: can a septum also be formed internally as part of an organ, that is, not by the fusion of two adjacent organs?

Yes, it can. This occurs in Brassicaceae, and also in some legumes. This may be what is called a false septum. It is a cardinal organ part, and not a plant structure, so it will need to be named and defined separately. RW and DWS will look into this for next week.

The term "carpel septum" should be used to describe the false septum that separates a single carpel into mutilple locules, while "ovary septum" should be used to describe the septum that divides a multi-locular ovary that is part of fused gynoecium. Will change primary name of carpel septum (PO:0005009) to ovary septum.

stomatal meristemoid cell and meristemoid/initial cell

TAIR has requested the term "stomatal meristemoid cell". guard mother cell develops_from stomatal meristemoid cell.

Right now, guard mother cell (PO:0000351) develops_from meristemoid cell (PO:0000070) and also develops_from epidermal initial (PO:0000349).

Suggestion: -define initial cell as a meristematic cell that by division, gives rise to two cells, one of which remains meristematic, while the other is added to the plant body.

Suggested new def'ns:

- meristematic cell: okay as is, but change from part_of meristem to meristem has_part meristematic cell (since not all meristematic cells are part of a meristem -- we can discuss this)

- meristemoid: A meristematic cell that is part of a portion of tissue that is composed mostly of somewhat older, differentiating cells.

- initial cell: A meristemoid that by (uneven?) division gives rise to two cells, one of which remains meristematic, while the other is added to the plant body.

- epidermal initial: An initial cell that is part of an epidermis and gives rise to specialized cell types of the epidermis. Synonym: epidermal initial cell

New term:

stomatal initial/stomatal meristemoid: An epidermal initial that undergoes several rounds of uneven division, each time giving rise to a larger daughter cell that differentiates into an epidermal ground cell and a smaller daughter cell that remains meristematic, until the meristematic cell differentiates into a guard mother cell.

stomatal initial will be primary name, stomatal initial cell and stomatal meristemoid will be synonyms.

>>It might also be better to merge meristemoid and initial cell, rather than keeping them as separate classes. Meristemoid has no other children besides initial cell. Are they the same thing?

We will merge initial cell and meristemoid, keeping initial cell as primary name.

Proposed def.: A meristematic cell that by division gives rise to two cells, one of which remains meristematic, while the other is added to the plant body.

Comment: Initial cells are part of a portion of tissue that is composed mostly of somewhat older, differentiating cells. The division of an initial cell is often uneven, with the smaller daughter cell remaining meristematic.

xylem pole pericycle cell

The term 'xylem pole' refers to a column of xylem running through the root stele and xylem pole pericycle cells are pericycle cells adjacent to the xylem cells

- xylem pole pericycle cell: A pericycle cell that is adjacent to a xylem cell.

Comment: Xylem pole pericycle cells may retain some meristematic activity and are the site of lateral root initiation. ref: PMID: 17993548

Suggest new term:

- pericycle cell: A ground tissue cell that is part of a pericycle.

Suggested def'n:

- phloem pole pericycle cell: A pericycle cell that is adjacent to a phloem cell.

Comment: Phloem pole pericycle cells are distinct from xylem pole pericycle cells in that they display cytoplasmic characteristics of a more differentiated status. ref: PMID: 17993548

These terms and definitions were accepted as suggested.

Other

Renamed terms

• cultured somatic plant embryo (PO:0000011)

• nucellar plant embryo (formerly adventitious embryo)(PO:0004537)

Renamed parts of the anther wall:

(also added pollen sac… as synonyms for all of these)

-Endothecium (PO:0020002) > anther wall endothecium (needs new definition – not a hypodermis)

-Exothecium (PO:0020004) > anther wall exothecium

-Middle layer (PO:0004700) > anther wall middle layer (definition needs work)

-primary parietal cell layer (PO:0006006) > anther wall primary parietal cell layer (definition needs work)

-secondary parietal cell layer (PO:0006007) > anther wall primary parietal cell layer (definition needs work)

-inner secondary parietal cell layer (PO:0006008) > anther wall inner secondary parietal cell layer (definition needs work)

-outer secondary parietal cell layer (PO:0006009) > anther wall outer secondary parietal cell layer (definition needs work)

-tapetum (PO:0009071) > anther wall tapetum

Changed primary name of bud scale (PO:0020054) to bud scale leaf.

Added "leaf, vascular" and "scale-like leaf" as synonyms of vascular leaf.

Added a bunch of adjective/noun synonyms. For example, archegonium egg cell as synonym for archegonial egg cell, antheridial jacket layer as synonym of antheridium jacket layer. At some point, the names should be normalized.

Miscellaneous Changes

Made pollen sac part_of microsporophyll, instead of part_of anther, and added anther has_part pollen sac.

Made anther wall is_a microsporangium wall

Made nucellar epidermis (PO:0008006) is_a megasporangium exothecium

Removed anther wall tapetum develops-from anther wall inner secondary parietal cell layer. Made is_a microsporangium tapetum.

Removed modified aleurone part_of aleurone layer, because it was already is_a aleurone layer.

Added Spanish synonyms for plant cell and plant embryo, but accented characters don't display properly in Amigo.

Added "portion of … tissue" as synonyms to several tissue types of tissue that had single word names (like epidermis, collenchyma).

• Changed names of child terms of sporangium/spore capsule:

PO:0025093 Moss capsule annulus > spore capsule annulus

PO:0025231 Moss capsule columella > spore capsule columella

PO:0025229 Moss capsule valve>spore capsule valve

Added anther lobe as narrow synonym of pollen sac. Was there on the old term, but didn’t get transferred when it was obsoleted and replaced.

Made theca is_a collective organ part structure, part of anther, has_part pollen sac.

Made microsporocyte part of microsporangium, instead of part of microsporocyte. Made sporocyte part of sporangium.

Added synonyms to vascular leaf (frond, needle-like leaf) and non-vascular leaf (phyllid, gametophyll, gametophytic leaf).

Moved juvenile, transition and adult leaf from vascular leaf to leaf. Also simple leaf and compound leaf.

Moved leaf aerenchyma, leaf mesophyll, leaf lamina, leaf margin, leaf intercalary meristem and leaf sheath from part_of vascular leaf to part_of leaf.

Moved leaf endodermis from part_of leaf to part_of vascular leaf.\

Add subsets for bryophytes, pteridophytes and gymnosperms (in addition to angiosperms)

Add new relation participates_in

Removed has_part relations from all pairs of terms that has reciprocal has_part/part_of relations

Updated definition of radicle. Removed radicle part_of embryo axis, added embryo axis has_part radicle.

Updated definition of hypocotyl and made it is_a stem internode, instead of is_a cardinal organ part.

Updated definition of epicotyl and made it is_a stem internode, instead of is_a embryonic plant structure.

Made hypocotyl-root junction is_a cardinal organ part. Already part of embryo axis.

Made mesocotyl is_a stem internode. Did not change definition, need to wait for discussion.

Made embryonic leaf is_a leaf, part_of embryo.

Made plumule is_a terminal bud, part_of embryo.

Made scutellar node is_a stem node, part_of embryo axis.

Added formal relations for: sporophyte replaced_by saprophytic phase and gametophyte replaced by gametophytic phase. Couldn't do this for the previous release because of separate files. Did not add replaced by relation for seedling, b/c there is not seedling phase yet.

Updated definition of embryo sac.

Updated definitions of archegonium egg cell, embryo sac egg cell, antheridium sperm cell, and pollen sperm cell

Added vascular leaf and non-vascular leaf part_of vascular and non-vascular shoot system, respectively.

Changed embryo to plant embryo.

Removed embryonic axis has_part radicle, has_part hypocotyl, has_part epicotyl, hypocotyl-root junction, has_part root meristem (b/c not true in all plants)

Added prothallium as narrow synonym of whole plant.

Added appropriate subsets for apical cell terms and other terms.

Changed theca (PO:0009069) to anther theca

Made sporangium (PO:0025094) is_a plant organ instead of is_a cardinal organ part.

Made female archesporial cell (PO:0006015) and male archesporial cell (PO:0006014) children of archesporial cell (PO:0030056)