Plant growth hormone is focus of Chinese research

Group led by Hongwei Guo, of Peking University, obtains important results in a study of the functioning of phytohormones, which regulate fruit maturation and defend against pathogens.

By Heitor Shimizu, in Beijing

Agência FAPESP – A group of researchers at Peking University aims to uncover how hormones function in plants. Their highly promising research findings have appeared in scientific journals including Cell Research, a publication of the Nature group, and The Plant Cell.

“The growth and development of plants is extensively modulated by many endogenous factors, including a type of small molecules known as phytohormones,” said Hongwei Guo, a professor at the College of Life Sciences, Peking University, who is one of China’s leading experts in plant genomics and proteomics.

“One of these phytohormones is ethylene, a gas molecule that regulates a wide range of processes, including fruit maturation, leaf and flower senescence, stress tolerance and defense against pathogens,” Guo explained.

Ethylene (or ethene) – a hormone present in plants and some fungi – is a hydrocarbon consisting of two carbon atoms and four hydrogen atoms (C2H4). It is a highly flammable, colorless gas with a somewhat sweet odor.

Ethylene is an important raw material in the chemical industry, used in the synthesis of products such as ethanol and in manufacturing a variety of plastics. It is also used to speed up the maturation of fruits such as bananas and to improve the color of oranges.

“One fundamental question in plant biology is how plants respond to various hormones at the physiological, morphological and molecular levels. And another important question is the interplay between these phytohormones, whether they act in parallel, cooperatively or antagonistically,” Guo said.

His group uses approaches in molecular genetics, biochemistry, genomics, bioinformatics, systems biology and chemical biology to investigate the signaling mechanisms and regulatory pathways of phytohormones, and ethylene in particular.

According to Guo, although the genetic process of ethylene signaling is reasonably well-known, the biochemical and regulatory aspects of each stage or component of the process are as yet poorly understood.

“We have studied factors that mediate the regulation of plant responses to ethylene, such as interaction with other phytohormones or reaction to environmental signals, especially light. These interactions point to the existence of complex signaling pathways through which ethylene acts on plants,” said Guo. Among the other hormones mentioned by the researcher were cytokinins, auxins and gibberellins.

“In studying the molecular and biochemical mechanisms of the relationships between different phytohormones and between these hormones and light, we found that the transcription factors known as EIN3 and EIL1 represent a fundamental integration with the interplay between ethylene and other phytohormones,” he noted.

Transcription factors are proteins that bind to DNA in eukaryotic cells to form a link between the RNA polymerase enzyme and the DNA. When these factors were suppressed, the Peking University researchers observed changes in the plant development processes.

“Our research introduces a molecular structure for how plant growth and development is controlled by phytohormones,” Guo said. The researchers use plants of the genus Arabidopsis, frequently used as a reference model for studying plant genetics.

The group has set up a database with the results of their studies, bringing together a large amount of experimental data and information on computational analyses. The Arabidopsis Hormone Database (AHD: http://ahd.cbi.pku.edu.cn/) is open to consultation by any interested researcher.

The Peking University researchers plan to assemble an atlas of phytohormone biology and produce theoretical models that can be used to describe, verify and predict the operation and actions of these hormones.