#apomixis

Sure this is Spiranthes cernua, and we might be able to agree on that concept; or can we? 

Spiranthes cernua is a species that perhaps fits the concept of intermediate abrupt speciation more than most species fitting into the contemporary and distant past time slot so much so that it may be the next new model speices. 

Here is an R. A. style blurb that I plan on highly modifiying before the end of september as I collect more photos and take more photos of specimens. I also want to add article statements on each microspecies and add several method sections. I hope y’all enjoy this. 

Abstract:

Spiranthes cernua has been problematic for taxonomists for more than 100 years and is constantly having species being added or removed to its aggregate taxon. Spiranthes cernua complex is a consistent topic for debate: to resolve taxonomic issues, discuss hybridization and abrupt speciation, and view apomictic strategies for colonialization and genetic persistence. The focus of this paper is on apomictic persistence and the mechanism as a potential point of discussion for the persistence of hybrid populations, autopolyploid populations that are used as hypothetical taxonomic units , and for the idea of discussing it as potential model species for apomixis studies.

Indroduction:

Orchidaceae, Spiranthes spp. and Spiranthes cernua:

Orchidaceae is a nested taxon, specifically ‘the orchid family’ and it’s derivatives; Orchidaceae is a vastly complex group located within’ the Lilianae super order (Monocots, characterized monocotyledon), taxon, and is perhaps one of the most discussed families for a number of reasons: discussed for it’s number of species, it’s families distribution, it’s morphological adaptations, symbiotic ‘strategies’, phenology and life stages, associated pollinator syndromes, and the reproductive abilities known(Catling, 1982)(Dressler, 2005). All of which may be considered concepts that are driving factors for evolutionary success or failures according to Dr. David Briggs and Dr. Stuart M. Walters (Briggs and Walters, 1969-2016). North America is considered the center for Spiranthes spp. diversity, with potential to expand this specific genera’s diversity and thus expand Orchidaceae too (Sheviak and Catling, 1980) (Dueck et. al. ,2005). Orchidaceae can be further broken down from subfamilies to tribes and tribes to genera with specific species and their subspecies, botanical varieties, isolated forms, mutation forms, and cytotypes; scrutinized complex resolution and the discovery of new species may disrupt the historic validity of sources,  an approximate number may be 24,500 Orchidaceae members, unique enough to be species, currently inhabiting the globe(Dressler ,2005) )(Taylor et. al. ,2007-2009) (Dueck et. al., 2015).  In the United States, Spiranthes spp. is one such genera in the Orchidaceae that is known for it’s apomictic behavior to some extent, and is distributed across the United States, found in every state except for Hawaii, and distinguished to have ~ 45 species present standing (Catling and Richard, 1980)(Catling, 1981/1982)(Catling and Brown, 1983)(Argue, 2011). Spiranthes spp., in general, is “The most diverse species in Eastern North American flora” and Spiranthes cernua seems to be at the center of this issue (Sheviak and Catling, 1980) (Sheviak, 1982/ 1991). Spiranthes cernua, colloquially ‘the nodding ladies’ tresses’, has been a major subject of taxonomic study, evolutionary origins, and molecular and genetic study as a species noted in North America’s flora (Dueck et. al., 2005) (Dueck et. al., 2015) (Pace and Cameron, 2017). Though difficult to grow from seed, tissue cultures are a process widely used in the cloning of orchid species and can be done on a massive scale; “Spiranthes cernua is a facultatively agamospermic polyploid compilospecies in which unidirectional gene flow from related diploids generates a wide range of novel forms and races” and could be potential model species for apomixis research based on model species criteria (Briggs and Walters, 1969-2016) ( Griesbach, 1986) ( Gonzalez and Concha et. al., 2002) (Dueck et. al., 2014). What is known from Spiranthes cernua’s apomixis habit is critical to understand to make conclusions on potential driving factors for Spiranthes spp. speciation events as a whole is definitely key to understanding species diversity.

 Morphological Representation in Spiranthes cernua:

Spiranthes cernua is as morphologically diverse as it is distributed, and ecotypes from specific ecoregions are still not enough to truly represent a limit to the morphology present (Dueck et. al., 2014). One perceived problem with specific statewide flora’s can have different mechanisms for how they describe this species with overlap and in some cases federally threatened designation is ‘potentially’ not placed due to the var. or form maintaining it’s status as Spiranthes cernua, making studying Spiranthes cernua critical to conservation in the genus (Dueck et. al., 2014). Morphological characteristics that are critical to arriving at an ~ identification is somewhat associated with the minimum need that a basal rosette is present with no cauline patterning present, a single rachis like spike as an inflorescence is present and grows directly from the basal rosette, rachis is pubescent to canescent( densely pubescent to some degree), but not hirsute( densely pubescent with large hairs); hairs along the inflorescence are mixed in form: “trichomes capitate, glands obviously stalked” (Sheviak and Brown, 2002). The nod and flower color, leaf morphology, floral tube morphology, all display differences in populations, though they are usually completely white, creamy, or silverfish in sheen, instead of having yellow or green tints (Sheviak and Brown, 2002).  The nod that occurs is caused by the reflexing at the base of the perianth; however, the exaggeration of the nod is variable (Sheviak and Brown, 2002).

 Apomixis and it’s Potential:

Apomixis is a complicated asexual regenerative behavior that certain plant species undergo and is widely accepted as one of many successful reproductive mechanisms that has developed many times over history(Walters and Briggs, 1969-2016). Apomixis, through agospermic seed setting, is considered a pseudo-selfing mechanism that appears to parallel with cleistogamous mechanisms; however, mechanically it is different as gametogenesis and reduced tissue structures under scrutiny are less associated ,or not at all, with the ladder, and even delineated, to cell type generation from previously developed tissue types without reduction; in this way, it isn’t necessarily a ‘self-fertilizing’ event that creates offspring, but cellular propagation from a vegetative part of the original organism to produce seed(Walters and Briggs, 1969-2016) (Sharma and Thorpe, 1995). Another way to term apomictic mechanism for “Pathenogenetic seed setting” is “adventitious embryony”, “gametophytic apomixis”, and “asexual embryogenesis” (Sharma and Thorpe, 1995). Asexual propagation from non-reproductive vegetative organs as an inclusion in the concepts behind the definition of apomixis is notable, clarification of this type of apomixis, or vivipary, needs to be separated out in the definition for discernible definitions(Walters and Briggs, 1969-2016)(Sharma and Thorpe, 1995)(Carneiro et. al., 2006). The exception for the term ‘apomixis’ including asexual propagules, vegetative apomixis, comes from the idea that a species may not be able to set seed and only survives from this form of clonal propagation from a non-seed vegetative organ (Walters and Briggs, 1969-2016). Both forms are considerably advantageous to some degree, theoretical examples are areas where introduction events may occur and founders’ effects may be avoided (Walters and Briggs, 1969-2016) (Sharma and Thorpe, 1995). If we factor in allopolyploidy, which is considered a potential driving mechanism for speciation, or aiding to back up hypotheses delineating species (Walters and Briggs, 1969-2016). In North America we do see Spiranthes spp. exhibit polyploidy mechanism as the genus; a bimodal distribution of chromosome numbers becomes apparent from statistical analysis done from North American operational taxonomic units as a cohort: “two groups having either a base number of  n  = 15 or 22 (except for one with 12), or are amphiploid products of hybridization between members of the two groups (i.e., n  = 15 + 22) and thus also allopolyploids”(Dueck et. al., 2014). Many known examples of allopolyploidy have already been noted in Spiranthes cernua complex and evolutionary developments may occur in temporal span from a potentially speciating specimen that persists by these apomictic mechanisms in new environments until other evolutionary driving events occur like polyploidy events; and if these events have already happened, they can be persist in a population due to this mechanism (Walters and Briggs, 1969-2016) (Dueck et. al., 2014).

Reproductive output and phenology in Spiranthes cernua:

In populations, environmental factors and life cycles may need to be analyzed in this complex to isolate how much apomixis is associated with a populations success and this can be done to some extent by juxtaposing resource availability and allocation and its contribution to normal reproduction and apomictic reproduction; reproductive output, resource allocation costs in reproduction, in many species is considered to be a factor in measuring fitness (Walters and Briggs, 1969-2016) (Antlfinger and Wendel, 1997). In most taxon, and at least historically speaking, the view of reproductive output is viewed as a compromise in usable energy for species survival; however, “Positive rates of net photosynthesis by reproductive structures have been measured in many species ,including orchids” (Antlfinger and Wendel, 1997). Long term phenology studies of a specific population adds a certain level of approximation to reproductive output or at the very least the methods used may be used as a guide to further studies on the Spiranthes cernua complex; methods included were: fire studies, morphological assays, gas exchange surface area assays, plant growth assays, and chlorophyll assays (Antlfinger and Wendel, 1997).

Spiranthes cernua complex, hybridization, and apomictic events:

Hybridization, polyploidy events, cleistogamous crossing, apomictic progression, and cryptic origins are all present in Spiranthes cernua (Pace and Cameron, 2017). These sets of irregular population hereditary persistence phenomena, peloria, can occur in different rates at the same time in any specific population (Pace and Cameron, 2017). “Complicated set of issues is further obfuscated by the lack of a universally accepted species concept” (Pace and Cameron, 2017).  Legitimate species diagnosis specifically seems to have troubles with overlapping species or those closely related; Spiranthes cernua is known to hybridize and are related to S. magnicamporum, S. caesi, S. odorata, S. parksii, and S. ochroleuca with the level of hybridization varying and the level of polyploidy outcomes varying to the extent isolating a hybrid becomes difficult and complex ( Pace and Cameron, 2017). Combinations of methods are used, being critical to OTU sequences (from plastids, mitochondria, and nuclear DNA) ,specific to a standing/~delineate species, and using morphology from records of these OTU done by taxonomic analysis and utilizing matrix comparisons of a hybrids’ amplified fragment length polymorphism, present, and juxtaposing them to theorized parent species (Dueck and Fowler et. al., 2005) (Pace and Cameron, 2017). Synonymous taxonomical groupings have been made and removed due to hybrid history, and contemporary hybridization, with discernable amounts of claims on polyphyletic and paraphyletic linking being focused on; although clade crossing, reticulation, occurs enough to disrupt delineation(Pace and Cameron, 2017). This concept becomes an issue when planning out state resources and monitoring of federally threatened taxa; S. parksii is an example of federally threatened taxa that is now under scrutiny of placement under S. cernua, “as a localized sub-peloric form promulgated through apomixis” (Pace and Cameron, 2017). Spiranthes cernua complex apomixis events does not stop being present in operable resolution of hybrid origin’s and species housed under this complex (Pace and Cameron, 2017). Several other species in this complex are known to have levels of apomixis effecting their population occurrences and evolutionary history: S. casei, S. incurve (a polyploid hybrid originated species between S. cernua and S. magnicamporum), and S. ochroleuca (Dueck and Fowler et. al., 2005) (Pace and Cameron, 2017). These are noted as “micro species” of S. cernua in the complexes case; S. casei and S. incurve are specific micro species components that show a trend of majority apomictic population growth in comparison to those that have more mixed stratification of crossing habit seed setting and apomictic persistence (Pace and Cameron, 2017). S. xkapnosperia, which has distinct components from accepted S. ochroleuca, is another current hybrid that has questionable taxonomic stratification and phylogenetic presence that seems to follow trends of apomictic growth; but, population persistence is questionable as it stands( Pace and Cameron, 2017).

Conclusions:

Apomixis in Spiranthes cernua species complex does not successfully delineate one species, micro species, from the other as a solitary mechanism of evolution; instead evolution within this complex can be viewed as incorporating apomixis in high levels as a means to justify a hypothesis and describe evolutionary trends in species. The evolutionary developements in Spiranthes cernua complex usually are a factor of both facultative apomixis and some level of polyploidy event or hybridization event. Since apomictic linages are persistent in preserving genetic trends and occur in a common frequency in certain members of Spiranthes cernua complex, these members are good examples to study the driving mechanisms of apomixis. Some species in Spiranthes cernua complex may be cloned from tissue culture in mass utilizing well known orchid tissue culture methods. A combination of tissue culture and the frequency of apomixis as a strategy for maintaining characteristics in a population make this species concepts’ members potential model organisms to study apomixis as a mechanism for evolution.  

           Work cited:

Web references, Journal articles, R.A., and Taxon Sources:

Antlfinger, A. and Wendel, L.“Reproductive Effort and Floral Photosynthesis in Spiranthes Cernua (Orchidaceae)”. 1, June. 1997. American Journal of Botany Vol. 84, No. 6, pp. 769–780. https://doi.org/10.2307/2445813

Argue, C. L. “Subtribe Spiranthinae”. 18, August. 2011. Springer. The Pollination Biology of North American Orchids. Vol. 2, pp 19-52. https://link.springer.com/chapter/10.1007/978-1-4614-0622-8_2

Carneiro, V. T. C.; Dusi, D. M. A.; and Ortiz, J. P. A. “Apomixis: Occurrence, Applications and Improvements”. 2006. GSB. Floriculture, Ornamental and Plant Biotechnology. Vol 1, pp. 555-571. http://www.globalsciencebooks.info/Books/images/FOPBVolume1sample.pdf

Catling, P. M. “Breeding Systems of Northeastern North American Spiranthes (Orchidaceae)”. 1982. Canadian Journal of Botany. Vol. 60, No. 12, pp. 3017-3039. https://doi.org/10.1139/b82-358

Corrias, S. D. and Villa, R. “Embryology and Embryogenesis of Spiranthes L.C.M. Richard (Orchidaceae): S. spiralis (L.) Cheval and S. aestivalis (Poiret) L.C.M. Richard”. 1983. GBI. Vol. 117, No. 5-6 pp. 193-200. https://doi.org/10.1080/11263508309427969

Dressler, R. L. “How Many Orchids”. 2005. Selbyana. Vol. 26, No. 1, pp. 155-158. https://www.jstor.org/stable/41760186

Dueck, L. A. ; Aygoren, D.; and Cameron, K. M. “A Molecular Framework for Understanding the Phylogeny of Spiranthes (Orchidaceae), A Cosmopolitan Genus with a North American Center of Diversity”. 1, September. 2014. Wiley. American Journal of Botany. Vol. 101, No 9, pp. 1551-1571. https://doi.org/10.3732/ajb.1400225

Dueck, L. A.; Fowler, J. A.; et. al. “Genetic Discrimination of Spiranthes Cernua Species Complex in South Carolina”. 2005. Selbyana Vol. 26, No. 1, pp. 145-154. https://www.jstor.org/stable/41760185

Griesbach, R.J. “Orchid Tissue Culture”. 1986. Springer, Dordrecht. Current Plant Science and Biotechnology in Agriculture. Vol. 2, pp. 343-345. https://doi.org/10.1007/978-94-009-4444-2_29

Loyet, C. D. “Breeding Systems in Spiranthes magnicamporum (Sheviak)”. 1993. Masters Theses 2179. EIU. The Keep. https://thekeep.eiu.edu/theses/2179/

Nygren, A. “Apomixis in the Angiosperms II” December. 1954. Vol 20. No 10, pp. 577-649. https://www.jstor.org/stable/4353528

Pace, M. C. and Cameron, K. M. “The Systematics of the Spiranthes cernua Species Complex (Orchidaceae): Untangling the Gordian Knot”. 27, December. 2017. ASOPT. Systematic Botany. Vol 42, No. 4, pp. 640-669. https://doi.org/10.1600/036364417X696537

  Schmidt, J. M. and Antlfinger, A. E. “The Level of Agospermy in a Nebraska Population of Spiranthes cernua (Orchidaceae)” 1, May. 1992. Wiley. American Journal of Botany. Vol. 79, No. 5, pp. 501-507 https://doi.org/10.1002/j.1537-2197.1992.tb14585.x

Sharma, K. K. and Thorpe, T. A. “Asexual Embryogenesis in Vascular Plants in Nature”. 1995. SSBMD. Current Plant Science and Biotechnology in Agriculture: In Vitro Embryogenesis in Plants, Vol 20, pp 17-72. https://link.springer.com/chapter/10.1007/978-94-011-0485-2_2

Sheviak, C. J. and Brown, P. M. “Orchidaceae: Spiranthes cernua”.1, June. 2002-2003. MOBOT, New York and Oxford. FNA: Vol. 26, pp. 498-499, 530-537, 541-542. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242101948 and http://beta.floranorthamerica.org/Spiranthes_cernua

Sheviak, C. J. and Catling, P. M. “The Identity and Status of Spiranthes Orchroleuca”. October. 1980. JONEBC. Rhodora No. Vol. 82, No. 832 , pp. 525-562. https://www.jstor.org/stable/23314094

Sheviak, C. J. “ Biosystematic study of the Spiranthes cernua complex”. 1982. Bull. New York State Mus. Sci. Serv. pg 448. https://doi.org/10.5962/bhl.title.135544

Sheviak, C. J. “Morphological variation in the compilospecies Spiranthes cernua: Ecologically-limited Effects of Gene Flow”.1991. Lindleyana. Vol. 6, pp 228–234.

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 Book references:

The Scientific Research Notes of S. Sunkavally, Printed Part, Page. 35.

The Dawn of Self-Cloning Crops Imagine a future where farmers no longer need to purchase new seeds each planting season. Sounds like science fiction, right? Well, that future might be closer than you think. Researchers are making significant strides in developing self-cloning crops – plants that produce seeds genetically identical to the parent plant. This groundbreaking technology promises to…

What is Apomixis and What is its Importance in Plants?

In this tutorial, we have discussed “What is apomixis and what is its Importance in plants?” What is Apomixis The formation of new individuals through the normal process of sexual reproduction by the meiotic formation of gametes and their subsequent fusion during fertilisation is called amphimixis. The formation of new individuals through asexual reproduction without the formation and fusion of…

Apomixis bypasses meiosis to produce seed. And it is considered to bring economic benefits over than the “Green Revolution” by using to fixation of F1 variety in agriculture. In our laboratory, we have been successful in cloning the apomixis-specific gene of ASG-1, isolated from Panicum maximum. In order to do functional analysis of the ASG-1, we have been carrying out the gene transformation of ASG-1 in sweet potato, a vegetative reproductive crop. In this study, the purpose is getting transformants by using the seeds of sweet potato and the instrument of NEP21, an electroporation. As the first step, we used the Ipomoea nil cv. [Kitachiasagao] as stock and Ipomoea batatas (L.) cv. [Koganesengan], [Narutokintoki] and [Beniazuma] as graft to get seeds. And then, the transformants of GUS was induced into sweet potato seeds by using the instrument of NEP21. As the results, 1) according to the standard of selecting variety based on the cross incompatibility referred from Kyushu-Okinawa Agricultural Research Center, we selected 3 varieties out from 6 ones held; 2) according to the standard of selection suitable to be used as either seed side or pollen side, we have gotten matured seeds successfully from the 3 varieties; 3) using the sweet potato seeds collected and the instrument of NEP21, GUS gene expression was detected in the transformant by GUS dyeing with blue color appeared on the surface of the seeds and young buds.

Author(s) Details

Lanzhuang Chen School of Horticulture and Food Sciences, Minami Kyushu University, 3764-1, Tatenocho, Miyakonojo-City, Miyazaki, 885-0035, Japan.