Table II. Types of LDs in plants.
The information is simplified for generalization. Many exceptions are known. Less-studied LDs of special functions are not included. Sizes of LDs are greatly generalized to show differences among LD types. Comprehensive information on the distribution of nonoleosin LD proteins on various LDs is unavailable.
| Location/Name | Oleosin Lineages | Size (Generalized) | Morphology | Notable Biogenesis | Function (Projected or Proven) | Phylogeny Restriction | Additional Comments |
|---|---|---|---|---|---|---|---|
| μm | |||||||
| Seed LD | SH oleosin, SL oleosin U oleosin | 1 | Solitary, not aggregated | Released from the ER; degraded by cytosol lipase or engulfed by vacuoles | TAGs for gluconeogenesis during germination | All seed plants | Two oleosin isoforms could form a dimer |
| Pollen LD | U oleosin | 0.5 | Solitary, not aggregated | Transported along the cytoskeleton from pollen to tube tip | TAGs releasing FA for tube tip plasma membrane elongation | All seed plants | TAGs not for gluconeogenesis |
| Flower tapetosome | T oleosin | 5 | Cluster of alkane LDs and flavonoid vesicles | ER produces both oleosin-coated alkane LDs and flavonoid vesicles | Upon programmed cell death, LD alkane and flavonoid become pollen coat | Family Brassicaceae | In anther tapetum of only one family; with multitandem T oleosin genes |
| Aerial epidermis giant LD | U oleosin | 10 | Cluster of LDs and other vesicles, etc. | Have not been delineated | Hub of cuticle wax | Order Asparagales | In green aerial epidermis with thick cuticle of only one order |
| Fruit mesocarp large LD | M oleosin | 20 | Giant and small LDs, not aggregated | Small oleosin-coated LDs fuse with oleosinless giant LDs | Attract animals for seed dispersion | Many orders | Oleosin-coated small LDs found only in family Lauraceae (e.g. avocado) |
| Leaf, stem, root LD | Likely to have oleosin | 0.5 | Solitary, not aggregated | Not necessarily from ER budding | TAGs as refuge for toxic FFAs from damaged membranes upon stress or senescence; produce phytoalexin and brassinosteroids | All plants | Minimal number of LDs; induced by stresses and senescence |
| Rubber particle | No | 10 | Solitary, not aggregated | Released from cell upon wounding | Defense | Many orders | Polyisoprene instead of TAGs; two related proteins: SRPP and REF |
| Plastid plastoglobule | No | 2 | Solitary or associated with inner membrane | Released from plastid thylakoid membrane | Temporary refuge for toxic FFAs; fruit pigment to attract animals | All plants | Various neutral lipids: TAGs, carotenoids, etc. |