Transcriptome Analysis of Inflorescence Development at the Five-Leaf Stage in Castor (Ricinus communis L.)

The yield of castor is influenced by the type of inflorescence and the proportion of female flowers. However, there are few studies on the genetic mechanism involved in the development and differentiation of castor inflorescences. In this study, we performed transcriptomic analyses of three different phenotypes of inflorescences at the five-leaf stage. In comparison to the MI (complete pistil without willow leaves), 290 and 89 differentially expressed genes (DEGs) were found in the SFI (complete pistil with willow leaves) and the BI (monoecious inflorescence), respectively. Among the DEGs, 104 and 88 were upregulated in the SFI and BI, respectively, compared to the MI. In addition, 186 DEGs and 1 DEG were downregulated in the SFI and BI compared to the MI. Moreover, we conducted GO and KEGG enrichment analyses of the DEGs. In comparison to the MI, the SFI and BI exhibited the enrichment of functional branches in DEGs, specifically in pollen wall assembly, pollen development, and cellular component assembly involved in morphogenesis. In our study, RADL5 showed low expression levels between SFI-vs.-MI types. In addition, we found that the expression of NAC in the SFI differed from that in MI and BI, and some genes related to hormonal signaling changed their expression levels during inflorescence differentiation. These results reveal the genetic mechanism of sex genotypes in castor, which will not only guide researchers in the breeding of castor but also provide a reference for genetic research on other flowering plants.