Busan National University Professor Joraehyun's Team Identifies How Photosynthetic Product 'Sucrose' Promotes Flowering by Degrading Rice Flowering Repressor Protein

Regulation of Photosynthesis and Flowering Time in Food Crops
New Approaches Expected for Improving Agricultural Productivity

Pusan National University (President Choi Jae-won) announced on the 21st that Professor Cho Rae-hyun's research team from the Department of Plant Life Sciences has revealed that sucrose, a photosynthetic product commonly known as the main energy source for plants, also acts as a signaling molecule that promotes the flowering time of rice.

'Sucrose' is one of the major sugars produced through photosynthesis in plants, a disaccharide formed by the combination of the monosaccharides glucose and fructose. Sucrose supplies energy through cellular respiration and plays an important role in various developmental and physiological processes of plants.

Professor Cho Rae-hyun's team at Pusan National University conducted joint research with teams from Inha University and Kyung Hee University to elucidate the mechanism by which sucrose signaling regulates rice flowering and explained the new function of sucrose as a signaling molecule.

The flowering time of crops is one of the important research topics for improving crop productivity and quality.

The flowering time of crops significantly affects panicle formation, grain number, and quality. Early flowering can be advantageous for productivity by avoiding damage from high temperatures or typhoons. However, excessively early flowering risks reduced fertilization rates due to insufficient vegetative growth and cold damage, leading to decreased yield. Conversely, late flowering can avoid high temperatures and secure sufficient growth periods, but there are concerns about quality degradation due to cold damage or delayed maturation in the late maturation period (autumn).

Flowering at an appropriate time (considering temperature, humidity, photoperiod, etc.) plays a key role in determining crop productivity and quality. Therefore, it is necessary to optimize and coordinate the cultivation environment based on an understanding of crop flowering physiology. Especially nowadays, with increasing abnormal weather due to climate change, it is important to predict changes in flowering time accordingly and respond appropriately.

This study revealed that sucrose, a photosynthetic product, functions not only as a simple energy source but also as a signaling molecule that induces flowering in plants. The research team confirmed that sucrose promotes flowering by reducing the stability of a protein called ‘Ghd7’, which suppresses flowering in rice.

Ghd7, which stands for Grain number, plant height, and heading date7 protein, plays an important role not only in suppressing rice flowering but also in regulating seed yield and plant height.

At flowering time, the concentration of sucrose in the plant vascular system rapidly increases, suggesting a close correlation between sucrose concentration and flowering time; however, the molecular mechanism linking these phenomena has not yet been clearly elucidated. In particular, research on the role of sucrose in rice, a staple food crop, has been scarce.

This study found that when sucrose is supplied externally, the expression of genes promoting flowering increases, whereas in mutants unable to properly transport sucrose or in plants where sucrose degradation occurs excessively, intracellular sucrose concentration decreases, resulting in delayed flowering.

Notably, the research team identified the process by which the IPI1 protein degrades the flowering suppressor protein Ghd7 in response to high sucrose concentrations. These findings suggest that sucrose acts as an important signaling molecule regulating rice flowering time beyond being a simple energy source. This discovery is expected to provide a new approach to strategies aimed at improving agricultural productivity by linking photosynthesis and flowering time regulation in food crops.

Professor Cho Rae-hyun stated, “This study is significant in revealing that sucrose, a photosynthetic product, functions not only as an energy source but also as a signaling molecule regulating flowering time,” and added, “Based on these results, further research on the signaling functions of sucrose is anticipated.”

This research was supported by the Korea Research Foundation’s Mid-career Researcher Support Program and the Rural Development Administration’s Low-carbon Green Rice Production Technology Development Project. It was conducted jointly by Professor Cho Rae-hyun and doctoral student Baek Ki-beom from Pusan National University’s Department of Plant Life Sciences, Professor Yoon Jin-mi’s team from Inha University’s Department of Life Sciences, and Professor Ahn Jin-heung’s and Professor Jeon Jong-sung’s teams from Kyung Hee University’s Department of Genetic Engineering and Life Sciences.

The paper was published in the December 2024 issue of the internationally prestigious journal in the field of plant sciences, the Journal of Integrative Plant Biology.

(From left) Professor Jo Raehyun, PhD candidate Baek Kibum.

This content was produced with the assistance of AI translation services.