Plukenetia volubilis is a perennial oilseed vine and is monoecious, with separate female and male flowers on the same inflorescence.  

Researchers previously developed an efficient method to convert most of the male flower buds to female flower buds by exogenous 6-benzyladenine (6-BA) treatment. However, the gene expression information in florescence buds and the factors regulating floral sex in P. volubilis remain poorly understood. 

Prof. XU Zengfu and his team from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences conducted a study aiming to reveal sex differences in P. volubilis at the transcription level.  

They performed de novo transcriptome assembly and comparative analysis on control male inflorescence buds (MIB) and female inflorescence buds (FIB) induced by 6-BA using Illumina sequencing technology. 

More than 104.1 million clean reads and 57,664 unigenes were obtained from the two transcriptome libraries. The expression levels of PvoCKX1 and PvoAPT1 were down-regulated, whereas PvoARR9 was up-regulated in FIB, suggesting that cytokinin might play a positive role in female floral bud development, which occurs prior to the development of male floral buds in P. volubilis.  

Several genes, such as PvoGH3.1, PvoGH3.3, and PvoIAA14, were up-regulated in FIB. Therefore, an abundance of auxin signaling in FIB may potentially lead to female tissue development of P. volubilis. 

They also found that PvoERF109 and PvoERF017 were significantly down-regulated; however, PvoERF034 was up-regulated in FIB compared with MIB. 

The results indicated that the mechanism of sex differentiation in P. volubilis might be different from that of cucumber, melon, or Opuntia stenopetala. The crosstalk and balance of multiple phytohormones might affect sex differentiation in P. volubilis. 

The study entitled "De novo transcriptome assembly and comparative analysis between male and benzyladenine-induced female inflorescence buds of Plukenetia volubilis" has been published in Journal of Plant Physiology. 

Plukenetia volubilis  (Image by FU Qiantang)