Specific expression of apomixis-linked alleles revealed by comparative transcriptomic analysis of sexual and apomictic Paspalum simplex Morong flowers

Abstract

Apomixis is defined as clonal reproduction by seed. A comparative transcriptomic analysis was undertaken between apomictic and sexual genotypes of Paspalum simplex Morong to identify apomixis-related polymorphisms at the level of mRNA. cDNA-AFLP (amplified fragment length polymorphism) profiling of apomictic and sexual flowers at several stages of development yielded 202 amplicons that showed several kinds of expression specificities. Among these, the large majority consisted of amplicons that were present only in specific stages of development of the apomictic flowers. Ten percent of polymorphic amplicons were present with almost identical intensity in all stages of the apomictic flowers and never in the sexual flowers. Reverse transcription-PCR (RT-PCR) and Southern analyses of these amplicons showed that they belong to constitutively expressed alleles that are specifically present on the apomixis-controlling locus of P. simplex. The most frequent biological functions inferred from the sequence homology of the apomixis-linked alleles were related to signal transduction and nucleic acid/protein-binding activities. Most of these apomixis-linked alleles showed nonsense and frameshift mutations, revealing their probable pseudogene nature. None of the amplicons that were present only in specific stages of development of the apomictic flowers co-segregated with apomixis, indicating they did not originate from additional apomictic alleles but more probably from differential regulation of the same allele in apomictic and sexual flowers. The molecular functions inferred from sequence analysis of these latter amplicons were related to seed storage protein and regulatory genes of various types. The results are discussed regarding the possible role in apomictic reproduction of the differentially expressed genes in relation to their specificity of expression and inferred molecular functions.

Apomictic and Sexual Germline Development Differ with Respect to Cell Cycle, Transcriptional, Hormonal and Epigenetic Regulation

“…These play crucial roles in auxin-regulated gene expression, for example to control cell type-specific auxin responses during Arabidopsis embryo development [76], [77]. Evidence for differential expression of ARF genes has previously been reported during early stages of reproductive development in a comparative cDNA-AFLP analysis targeting sexual and apomictic Paspalum simplex flowers [35].…”

Characterization of retrotransposon sequences expressed in inflorescences of apomictic and sexual Paspalum notatum plants

“…In the past few years, several studies have been published which identify transcripts that are differentially expressed in reproductive tissues of apomictic and sexual plants (Rodrigues et al 2003;Albertini et al 2004;Laspina et al 2008;Cervigni et al 2008;Yamada-Akiyama et al 2009, Polegri et al 2010. All these articles were focused on the characterization of protein-coding transcripts and presented valuable evidence indicating that central pathways (i.e., ERK signaling, protein degradation, RNA transcription and DNA modification) were differentially modulated in agamospermic plants with respect to sexual ones.…”

Identification of Candidate Genes Related to Polyploidy and/or Apomixis in <i>Eragrostis curvula</i>

“…Sequences with similar annotations have been reported to be associated with apomixis and/or polyploidy for various other species, including Poa pratensis [53], Paspalum notatum [44,45], potato [54], Pennisetum squamulatum and Cenchrus ciliare [25], Panicum maximum [55], and Paspalum simplex [24,56]. Taking into account our previous results in E. curvula [32,33,35], the results of the present study, and those reported for other species by other authors, there are many commonalities among the different species with respect to apomixis.…”