Abstract
Pineapple plant usually has a capitulum. However, a fan-shaped inflorescence was exceptionally evolved in pineapple, having multiple crown buds. In order to reveal the molecular mechanisms of the formation of the fan-shaped inflorescence, fruit traits and the transcriptional differences between the fan-shaped inflorescence and the wild-shaped inflorescence pineapples were analyzed in three tissues, i.e., the flower stem apex, the base of the inflorescence, and the inflorescence axis. The weight (i.e., individual yield) of fan-shaped fruit is 4.5 times that of wild-shaped fruit；and non-significant difference in soluble solids, soluble sugar, titratable acid, and Vitamin C was found. Between the fan-shaped inflorescence and wild-shaped inflorescence, a total of 5370 differentially expressed genes were identified across the three tissues. Of these genes, there were 489 overlapping differentially expressed genes in all three tissue comparisons. Between the two pineapples, functional analysis indicated that 444 transcription factors and 206 inflorescence development-related genes were differentially expressed in at least one tissue comparison, while 45 transcription factors and 21 inflorescence development-related genes were overlapped across three tissues. Among the 489 overlapping differentially expressed genes in the three tissue comparisons, excluding the inflorescence development-related genes and transcription factors, 80 of them revealed a higher percentage of involvement in the biological processes relating to response to auxin, and reproductive processes. RNA-seq value and real-time quantitative PCR analysis exhibited the similar gene expression patterns in the three tissues. Our result provided novel cues for understanding the molecular mechanisms of the formation of the fan-shaped inflorescence in pineapple, making a valuable resource for the study of plant breeding and the speciation of pineapple.
Highlights
IntroductionA fan-shaped inflorescence was evolved in an exceptional material, having multiple crown buds
Except for the inflorescence and fruit morphology, no great difference in the organ structure of the inflorescences and the contents of soluble solids, soluble sugar, titratable acid, VC and water in fresh fruits were found between the two pineapples (Fig. 1a)
5769 differentially expressed genes (DEGs) were identified between different tissues within each pineapple, indicating that the regulatory pathway existed in the formation of the fan-shaped inflorescence in pineapple
Summary
A fan-shaped inflorescence was evolved in an exceptional material, having multiple crown buds. In the pineapple plantations, we found that up to 10% inflorescence axis of some Cayenne cultivars (i.e., ‘Smooth Cayenne’ and ‘Tainong 17’) were evolved into the fan-shaped inflorescences (fruits) at the inflorescence differentiation stage. Those inflorescence mutants are good materials for studying the formation and development of inflorescence, and the related gene regulation. For the molecular mechanisms of inflorescence formation, some known or potential transcription factors and transcription co-regulators (e.g., microRNAs and proteins) have been identified in the model plants (e.g., Arabidopsis thaliana and Oryza sativa), by transcriptome and gene analysis [3, 4]. The molecular mechanisms of these regulatory factors are not clear
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