Mechanism study and application of a plant elicitor - chitooligosaccharide
Heng Yin, Xiaoming Zhao, Yuguang Du^*

Liaoning Provincial Key laboratory of Carbohydrates, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023.
^*Corresponding Author: Tel: (+86 411) 8437 9061; Fax: (+86 411)8437 9061; E-mail: duyg@dicp.ac.cn

Abstract
Chitosan is one of the most abundant carbohydrate biopolymers in the world. Chitooligosaccharides prepared from chitosan is a potent plant elicitor. The efficacy of chitooligosaccharides on plant disease control and stress resistance was reported by numerous papers. Chitooligosaccharides plant growth promoters and bio-pesticides were developed and used in several provinces in China.

Based on our experiments and other literature, we conclude that there are six steps in the process of chitooligosaccharides activated plant immunity：chitooligosaccharides signal reception; secondary signal messengers (NO, H₂O₂…) activation; plant hormones (SA, JA, ET…) accumulation; defense signal transcuction; defense-related genes and proteins expression, defense reaction (secondary metabolites production, PR proteins expression, callose accumulation…).

Key Words: chitooligosaccharide; chitosan; elicitor; plant immunity; plant defense