Transcriptome Analysis During Tetrasporogenesis of Gracilariopsis lemaneiformis and Preliminary Study of the Expressions of Its Meiotic Genes

The transcriptomes of three different parts of the fertile tetrasporophyte of Gracilariopsis lemaneiformis, including tip (T), middle (M), and subjacent (S) parts, with a gradual tetrasporangium maturity were analyzed and compared to identify the genes involved in the process of tetrasporogenesis. The number of differentially expressed genes (DEGs) for the Gple-S versus Gple-T comparison was 10296, and the numbers of DEGs for the Gple-S versus Gple-M and Gple-T versus Gple-M comparisons were 7435 and 1337, respectively. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed, and the results showed the enrichment of 132 KEGG pathways (corrected P <0.05). A total of 58 DEGs related to meiosis were screened and blasted against 18 meiosis-related genes (dmc1, mlh1, mnd1, msh4, msh2, msh6, mre11, pds5, pms1, rad21, rad50, rad51, smc1, smc2, smc4, smc5, smc6, and spo11), including four meiosis-specific genes. The transcriptome comparison indicated that in the T part, the meiosis, ribosome, and RNA transport-related genes were mostly up-regulated compared with those in the other two groups. In the M part, the genes related to ribosomes and the endoplasmic reticulum were also up-regulated compared with those in the lower part. Finally, in the S part, the genes associated with photosynthesis were mostly up-regulated, which might be helpful to the recovery from spore formation and release.