Unravelling the transcriptional landscape of extracellular invertases across reproductive development

<p dir="ltr">In Arabidopsis thaliana, sucrose utilisation, metabolism and transport are key processes which are fundamental to overall plant development and reproductive fitness. A key step in the utilisation of these carbohydrate resources is sucrose hydrolysis in sink organs. This generates hexose for essential cellular activities and maintains the source-to-sink sucrose transport. Sucrose hydrolysis is carried out by the Cell Wall Invertase (CWIN) family. In reproductive tissues CWIN2 and CWIN4 are the primary sucrose hydrolysing enzymes. Consequently, these genes have been shown to play a major role in supporting and directing reproductive development. These roles are the result of both hexose production and unidentified sugar-signalling pathways. As such it is important to identify and characterise the mechanisms which direct expression of CWIN2 and CWIN4 in Arabidopsis flowers reproductive organs.</p><p dir="ltr">To date, a small cohort of transcriptional regulators have been identified based on their ability to modulate the expression of CWIN2 and CWIN4. However, the precise mechanisms by which the regulators are able to effect CWIN expression are unknown. The present study aims to elucidate these pathways by identifying and characterising transcription factors which are able to interact directly with the regulatory elements of CWIN2 and CWIN4. Over the course of this study, we show that Auxin Response Factor 8 (ARF8) is able to bind the upstream promoter regions of both CWIN genes in order to promote their expression. Further analysis shows that this regulatory interaction is under the influence of the floral development gene Crabs Claw (CRC). As a result, we are able to show that auxin-mediated CWIN regulation is responsive to key floral organ regulators which help to shape the carbohydrate and phytohormone landscape of developing reproductive organs. This discovery highlights the interconnectedness of auxin and sugar signalling pathways in Arabidopsis and opens the door for future work which may further clarify these dynamic and regulatory complex interactions.</p>