Cassava is a staple food for people in tropical and subtropical regions. However, its cultivation faces challenges such as disease susceptibility, post-harvest spoilage and low nutrient content. Breeding more resilient varieties is essential, but the plant's low female-to-male flower ratio directly limits seed production in both natural and hybrid breeding.

In a study published in Journal of Plant Growth Regulation, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences revealed the intricate molecular mechanism controlled by the plant hormone cytokinin that leads to the formation of more female flowers in cassava.

"For decades, breeders have known that applying cytokinin like the compound benzyladenine (BA) can promote female flowers," said PAN Bangzhen from XTBG. "But the 'how' remains a black box. Our study opens this box by revealing a complex regulatory network that translates a hormonal signal into a developmental switch."

Through comprehensive transcriptome sequencing on cassava inflorescence buds treated with BA, researchers identified a widespread reprogramming of the plant's genetic activity. They found 2,749 differentially expressed genes, along with 95 long non-coding RNAs (lncRNAs), 46 circular RNAs (circRNAs), and six microRNAs (miRNAs) that were activated or suppressed.

Researchers found that lncRNAs help modulate hormone signaling and homeostasis, while miRNAs regulate key genes involved in cytokinin metabolism and stress responses. They found strong correlations between circRNAs and their parent genes involved in hormone transport and related processes, suggesting that circRNAs participate in feedback mechanisms to fine-tune cytokinin distribution within flower buds.

This study provides a theoretical guidance for understanding and manipulating cassava flower development and sex determination at the molecular level.