AUTHOR=Jones Dallas C. , Zheng Wenguang , Huang Sheng , Du Chuanlong , Zhao Xuefeng , Yennamalli Ragothaman M. , Sen Taner Z. , Nettleton Dan , Wurtele Eve S. , Li Ling 

TITLE=A Clade-Specific Arabidopsis Gene Connects Primary Metabolism and Senescence

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00983

DOI=10.3389/fpls.2016.00983

ISSN=1664-462X

ABSTRACT=<p>Nearly immobile, plants have evolved new components to be able to respond to changing environments. One example is <italic>Qua Quine Starch</italic> (<italic>QQS</italic>, AT3G30720), an <italic>Arabidopsis thaliana</italic>-specific orphan gene that integrates primary metabolism with adaptation to environment changes. <italic>SAQR (Senescence-Associated and QQS-Related</italic>, AT1G64360), is unique to a clade within the family <italic>Brassicaceae</italic>; as such, the gene may have arisen about 20 million years ago. <italic>SAQR</italic> is up-regulated in <italic>QQS</italic> RNAi mutant and in the <italic>apx1</italic> mutant under light-induced oxidative stress. SAQR plays a role in carbon allocation: overexpression lines of <italic>SAQR</italic> have significantly decreased starch content; conversely, in a <italic>saqr</italic> T-DNA knockout (KO) line, starch accumulation is increased. Meta-analysis of public microarray data indicates that <italic>SAQR</italic> expression is correlated with expression of a subset of genes involved in senescence, defense, and stress responses. <italic>SAQR</italic> promoter::GUS expression analysis reveals that <italic>SAQR</italic> expression increases after leaf expansion and photosynthetic capacity have peaked, just prior to visible natural senescence. <italic>SAQR</italic> is expressed predominantly within leaf and cotyledon vasculature, increasing in intensity as natural senescence continues, and then decreasing prior to death. In contrast, under experimentally induced senescence, <italic>SAQR</italic> expression increases in vasculature of cotyledons but not in true leaves. In <italic>SAQR</italic> KO line, the transcript level of the dirigent-like disease resistance gene (AT1G22900) is increased, while that of the Early Light Induced Protein 1 gene (<italic>ELIP1</italic>, AT3G22840) is decreased. Taken together, these data indicate that <italic>SAQR</italic> may function in the <italic>QQS</italic> network, playing a role in integration of primary metabolism with adaptation to internal and environmental changes, specifically those that affect the process of senescence.</p>