Location: Corn Insects and Crop Genetics ResearchTitle: A clade-specific Arabidopsis gene connects primary metabolism and senescence Author
Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2016
Publication Date: 7/12/2016
Citation: Jones, D.C., Zheng, W., Huang, S., Du, C., Zhao, X., Yennamalli, R., Sen, T.Z., Nettleton, D., Wurtele, E.S., Li, L. 2016. A clade-specific Arabidopsis gene connects primary metabolism and senescence. Frontiers in Plant Science. 7:983. doi: 10.3389/fpls.2016.00983. Interpretive Summary: In order to manipulate agronomically important traits, we need to understand how proteins act in the cell. Proteins achieve this tremendous task through physical and chemical interactions. But our understanding of gene and protein functions that form metabolic pathways are limited as computational methods cannot have 100% accuracy and coverage. In this work, a plant gene, SAQR (Senescence-Associated and QQS-Related), is identified and analyzed both experimentally and computationally, and its metabolic role connecting to plant senescence is revealed.
Technical Abstract: Plants have to deal with environmental insults as they cannot move to escape from stressful conditions. To do so, they have evolved novel components that respond to the changing environments. A primary example is Qua Quine Starch (QQS, AT3G30720), an Arabidopsis thaliana-specific (orphan) gene that connects primary metabolism and adaptation to environment changes. AT1G64360, which we term SAQR (Senescence-Associated and QQS-Related), is unique to six species within the family Brassicaceae; as such, the gene may have arisen about 20 million years ago. SAQR is up-regulated under light-induced oxidative stress in the apx1 mutants, and up-regulated two-fold in QQS RNAi mutants. Overexpression lines of SAQR have significantly decreased starch content; conversely, in an SAQR T-DNA knockout line, starch accumulation is increased. In both mutants, QQS expression is similar to the non-transgenic controls. Meta-analysis of public microarray data indicates that SAQR expression is correlated with expression of a subset of genes involved in senescence, defense, and stress response. Histochemical experiments using SAQR promoter::GUS lines reveal that SAQR expression increases after leaf expansion and photosynthetic capacity have peaked, but prior to visible natural senescence. SAQR is expressed predominantly within the leaf vasculature, increasing in intensity as natural senescence continues, and then decreasing prior to death. Under experimentally-induced senescence, SAQR expression increases in vasculature of cotyledons but not in true leaves. In the SAQR knockout line, the expression of a dirigent-like disease resistance gene is increased seven-fold while the ELIP1 (early light induced protein1) light and oxidative stress-related gene is decreased four-fold. Taken together, these data indicate that SAQR may function in the QQS network, playing a role in its integration of primary metabolism with adaptation to internal and environmental changes, specifically those that affect the process of senescence.