Pathogen-induced changes in malate content and NADP-dependent malic enzyme activity in C3 or CAM performing Mesembryanthemum crystallinum L. plants

M. Libik-Konieczny,M. Nosek,E. Surówka,Z. Miszalski,S. Goraj

doi:10.1007/s11738-012-0945-7

Abstract

Changes in malate concentration and activity of NADP-dependent malic enzyme were observed as the effect of Botrytis cinerea infection of C3 or CAM-performing Mesembryanthemum crystallinum plants. Biotic stress applied on C3 plants led to increase in malate concentration during the night and in consequence it led to increase in Δ-malate (day/night fluctuations) in infected leaves on the 2nd day post infection (dpi). It corresponded with induction of additional isoform of NADP-malic enzyme (NADP-ME3). On the contrary, CAM-performing M. crystallinum plants exhibited decrease in malate concentration and decay in its diurnal fluctuations as a reaction to B. cinerea infection. This correlated with significant decrease in activities of NADP-malic enzyme isoforms on the 2nd dpi as well as no fluctuations in their activities on the 9th dpi. Presented results point out to differences between C3 and CAM plants in the direction of changes in primary metabolism providing energy, reducing equivalents and carbon skeletons for defense responses to halt the pathogen growth.

Highlights

Mesembryanthemum crystallinum L. is an annual halophytic plant that in its natural habitat shows seasonal shift from C3 type of photosynthesis to Crassulacean Acid Metabolism (CAM) (Winter and Holtum 2007) During CAM cycle, malic acid is accumulated in the vacuole as a central intermediary in the process of carbon assimilation during the dark and it is metabolized in the following light period (Cheffings et al 1997)
Due to ability to change the mode of CO2 fixation under specific environmental conditions like, for example, salinity, M. crystallinum was extensively studied in context of engagement of different abiotic stressors in photosynthetic metabolism transition (Bohnert and Cushman 2000)
One leaf of third whorl of M. crystallinum plants in C3 and in CAM stage was inoculated with solution without fungi spores (MOCK) or it was inoculated with solution containing B. cinerea spores (INF)

Summary

Introduction

Mesembryanthemum crystallinum L. (ice plant) is an annual halophytic plant that in its natural habitat shows seasonal shift from C3 type of photosynthesis to Crassulacean Acid Metabolism (CAM) (Winter and Holtum 2007) During CAM cycle, malic acid is accumulated in the vacuole as a central intermediary in the process of carbon assimilation during the dark and it is metabolized in the following light period (Cheffings et al 1997). Abstract Changes in malate concentration and activity of NADP-dependent malic enzyme were observed as the effect of Botrytis cinerea infection of C3 or CAM-performing Mesembryanthemum crystallinum plants. CAM-performing M. crystallinum plants exhibited decrease in malate concentration and decay in its diurnal fluctuations as a reaction to B. cinerea infection.

Results

Conclusion