Identification and Functional Characterization of Arabidopsis icl Mutant Under Trehalose Feeding in Light and Dark Conditions

Trehalose is a non-reducing sugar that plays an important role in plant growth and development. To study the role of trehalose on lipid metabolism and gluconeogenesis, Arabidopsis thaliana wild type (WT) and TreF (a line expressing trehalase) were grown on ½ MS medium with or without 100 mM sucrose and or trehalose in light or continuous darkness. In dark, trehalose leads skotomorphogenesis in WT seedlings and inhibits hypocotyl elongation without altering root growth. Then, a knock out mutant of icl (defective in isocitrate lyase/ICL) was identified in the SALK T-DNA insertion line, yet plants of this line were not altered with regard to growth on MS medium supplemented with or without trehalose in light condition, compared to WT. But the hypocotyl length of icl seedling was shorter than WT when grown on trehalose in darkness. The current data revealed that trehalose feeding altered seedling establishment in both WT and icl mutant. ICL enzyme activity measurement showed that the patterns of changes were similar in all treatments. Meanwhile, trehalose feeding reduced icl gene expression and enzyme activity. Trehalose fed seedlings demonstrated a high accumulation of total lipids in darkness. Also fatty acids level was higher in seedlings grown in darkness, compared with the light condition. Therefore, trehalose may inhibit lipid utilization by suppressing icl gene expression and enzyme activity and thus restrict the supply of carbon sources to the growing seedling. These observations confirm that trehalose regulates plant metabolism in both light and dark.