Abstract Detail

Evolutionary Developmental Biology (Evo-Devo)

Parihar, Bharti [1], Almeida, Ana Maria [2].

A Morphological and Molecular Approach Towards Plantlet Development in K. marnieriana.

The genus Kalanchoe Adanson consists of approximately 150 species distributed mainly throughout Madagascar, South and East Africa, and Southeast Asia. Kalanchoe is roughly divided into three taxonomic sections based on their photosynthetic carbon assimilation pathways. Most Section I (Kitchingia) species perform C3 photosynthesis, while Section II (Bryophyllum) species are obligate CAM performers, mostly photosynthesizing diurnally. In Section III (Eukalanchoe), species exhibit classic succulent-like photosynthetic habits, performing CAM exclusively at night. Asexual reproduction has evolved within Kalanchoe Section II species, and is commonly a result of plantlet development in margins of cladodes, flattened leaf-like stems. While separate genetic studies have suggested formation of plantlets within Kalanchoe results from cooption of organogenesis and embryogenesis developmental processes to cladode margins, these studies focused on few genes, and fall short of a complete explanation of how asexual reproduction is ectopically triggered, especially concerning facultative Section II species, capable of performing both sexual and asexual reproduction. During typical seed development, transcription factor LEC1 plays a crucial role in regulating expression of embryogenesis genes, and previous studies have shown that ectopic expression of LEC1 is capable of triggering embryogenesis on vegetative tissues of Arabidopsis thaliana. However, the mechanisms leading to ectopic expression of LEC1 are still unknown, especially in species with functional LEC1 genes. In order to further dissect mechanisms underlying asexual reproduction in the genus Kalanchoe, we first carried out detailed morphological analyses of Section II species K. marnieriana. About 20 cladodes were plucked from the parent and plantlet development was observed stereoscopically focusing on meristematic structures along the cladode margin from which plantlets develop. Observations covered approximately 18 days and major phenotypic changes were noted until the plantlet exhibited distinguishable cotyledons. Days of significant developmental change were noted as 1,3,5,7,9,11 and 15. For SEM, additional cladodes were plucked from the parent plant, and 3 replicates for each of the 7 significant growth days were imaged, further suggesting a trigger of the embryogenesis pathway leading to the development of seed-like embryos. Light microscopy further confirmed this observation by providing detailed analysis of the internal embryo morphology, especially the connection between embryo and the mother-plant. This morphological study of plantlet development in K. marnieriana is now serving as the basis for detailed molecular analysis, with special attention to the ectopic activation of embryogenesis genes at cladode margins.

1 - California State University, East Bay, Department of Biological Sciences, 25800 Carlos Bee Blvd, Hayward, CA, 94542
2 - California State University East Bay, Department Of Biology, 25800 Carlos Bee Blvd, Hayward, CA, 94542, United States

Keywords:
Asexual Reproduction
Kalanchoe
K. marnieriana
LEC1
bulbil
plant development
cladode.

Presentation Type: Poster
Session: P, Evolutionary Developmental Biology (Evo-Devo) Posters
Location: Virtual/Virtual
Date: Tuesday, July 28th, 2020
Time: 5:00 PM Time and date to be determined
Number: PEV010
Abstract ID:172
Candidate for Awards:None