Abstract
BackgroundThe pistil is an essential part of flowers that functions in the differentiation of the sexes and reproduction in plants. The stigma on the pistil can accept pollen to allow fertilization and seed development. Papaya (Carica papaya L.) is a dioecious plant, where female flowers exhibit normal pistil, while the male flowers exhibit aborted pistil at a late stage of pistil development.ResultsThe developmental stages of papaya pistil were analyzed after first dividing it into slices representing the primordium stage 1 (S1), the pre-meiotic stages S2, post-meiotic stage S3, and the mitotic stage S4. The SS scoring algorithm analysis of genes preferentially expressed at different stages revealed differentially expressed genes between male and female flowers. A transcription factor regulatory network for each stage based on the genes that are differentially expressed between male and female flowers was constructed. Some transcription factors related to pistil development were revealed based on the analysis of regulatory networks such as CpAGL11, CpHEC2, and CpSUPL. Based on the specific expression of genes, constructed a gene regulatory subnetwork with CpAGL11-CpSUPL-CpHEC2 functioning as the core. Analysis of the functionally enriched terms in this network reveals several differentially expressed genes related to auxin/ brassinosteroid signal transduction in the plant hormone signal transduction pathway. At the same time, significant differences in the expression of auxin and brassinosteroid synthesis-related genes between male and female flowers at different developmental stages were detected.ConclusionsThe pistil abortion of papaya might be caused by the lack of expression or decreased expression of some transcription factors and hormone-related genes, affecting hormone signal transduction or hormone biosynthesis. Analysis of aborted and normally developing pistil in papaya provided new insights into the molecular mechanism of pistil development and sex differentiation in dioecious papaya.
Highlights
The pistil is an essential part of flowers that functions in the differentiation of the sexes and reproduc‐ tion in plants
SEEDSTICK (STK), known as AGAMOUS-LIKE 11 (AGL11), is a D-class functional gene and transcription factor MADS-box family in the ABCDE model [6], which are essential for ovule development [7]
Stage 1 is the representative stage for flower primordium formation, the key stage for papaya sex determination when both male and female flowers are smaller than 1 mm in length
Summary
The pistil is an essential part of flowers that functions in the differentiation of the sexes and reproduc‐ tion in plants. Flowers are the reproductive organs of flowering plants, and their development involves complex regulatory processes. AG is a C-class functional gene in the ABCDE model of flower development [3, 4] and plays an important role in regulating the development of stamens and carpel primordia [5]. SEEDSTICK (STK), known as AGAMOUS-LIKE 11 (AGL11), is a D-class functional gene and transcription factor MADS-box family in the ABCDE model [6], which are essential for ovule development [7]. AGL11 plays an essential regulatory role in ovule development and seed formation in tomato, grape, rice, and other species [9, 10]. SlSUP is a SUP-like gene that is expressed exclusively in female flowers and involved in ovule development in white campion Silene latifolia Poiret [13]. Its overexpression affects the development of leaf and floral organs and plant height in tobacco [14]
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