Chin J Plant Ecol ›› 2009, Vol. 33 ›› Issue (4): 812-823.DOI: 10.3773/j.issn.1005-264x.2009.04.020

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FENG Yuan-Jiao, WANG Jian-Wu*(), LUO Shi-Ming   

  1. Institute of Tropical and Subtropical Ecology, South China Agricultural University, Guangzhou 510642, China
  • Received:2008-09-01 Revised:2009-03-15 Online:2009-09-01 Published:2009-07-30
  • Contact: WANG Jian-Wu


Aims Our objectives were to investigate temporal dynamics of the contents of direct defense chemicals (DIMBOA and total phenolics) and the expression levels of their corresponding key genes (Bx1, Bx9 and PAL), direct defense protein-related genes (PR-1, PR-2a and MPI), and indirect defense chemical volatile-related genes (FPS and TPS) in leaves and root systems of Zea mays seedlings under the application of exogenous jasmonic acid (JA) on leaf surface.
Methods Leaves of Z. mays cultivar Gaoyou 115 were treated with JA with concentrations of 1, 2.5, 5 and 10 mmol·L-1. We examined contents of the defense chemicals and expression dynamics of their synjournal-mediated genes, direct defense protein-related genes and indirect defense chemical volatile-related genes in both leaves and roots from 3 to 48 h after the application.
Important findings Exogenous JA application resulted in significant timing and concentration effects on the chemical defense response. Gene expression of Bx9 and PAL in the leaves could be induced 3 to 6 h after treatment, resulting in an apparent increase in the content of DIMBOA and total phenolics. The increase was positively correlated with JA concentrations, but the inductive effect gradually decreased afterward. Gene expression of PR-2a and MPI in the leaves was also dramatically induced by JA up to 24 and 48 h, respectively. High JA concentrations induced the expression of FPS gene, whereas low JA concentrations had inducible effects on the expression of TPS after 3-6 h. In addition, JA treatment to leaves could indirectly induce the defense response in roots. Most parameters measured in the indirect induction mainly occurred in the later phase (after 24-48 h) of the treatment. For example, JA systematically increased the contents of DIMBOA and total phenolics in the roots and enhanced the expression of PR-2a, MPI, FPS and TPS genes in the roots 48 h after the treatment, showing a tendency of positive relationship with JA concentrations. These findings provided evidence that the indirect induction by JA application to Z. mays leaves on roots was not as strong as on leaves. Leaves started the defense response earlier than roots, and the induction of defense response both in leaves and roots was increased with increasing JA concentrations.

Key words: Zea mays, jasmonic acid, induced defense, timing and concentration effects