Transcriptome profile analysis reveals the regulation mechanism of pistil abortion in Handeliodendron bodinieri

Abstract

Handeliodendron bodinieri is a rare and endangered plant that belongs to the family Sapindaceae. H.bodinieri is also a Chinese endemic dioecious tree/shrub with multifunctional applications in the fields of landscape, medicine and bioenergy (biodiesel production). H. bodinieri has unisexual flowers with an aborted pistil and stamen, which makes it an excellent model to explore sex differentiation and unisexual flower development in a woody tree. This study investigates the critical stage, process, and molecular mechanism of pistil abortion, leading to gender differentiation, using paraffin section and RNA-seq technology. The results, which led to a better understanding of the phenotypic characteristics during the pistil abortion process, demonstrated that pistil abortion occurred during the development of the ovule, i.e., from the two-nucleate embryo sac to the four-nucleate embryo sac in stage one (the diameters of the flower buds were 1.3–1.6 mm). At this stage, male flower pistils appeared to be thinner, shriveled, dark-colored, and less swollen than female flower pistils. Furthermore, using the RNA sequencing technique, a comparison of male and female flowers was made before and after abortion. It was revealed that 12 genes related to ovule development, such as INO, BEL1 and CRC, 24 genes related to plant hormones, such as AHP6, ARF, ERF and GID1, and 12 genes related to ROS, such as POD, SOD, CAT and RBOH, could be involved in the regulation of pistil abortion. Therefore, this study will provide a theoretical foundation for future conservation, breeding and application of H. bodinieri.