The QQS orphan gene of Arabidopsis modulates carbon and nitrogen allocation in soybean

Abstract

<p>The genome of each species contains as high as 8% of genes that are uniquely present in that species. Little is known about the functional significance of these so-called species specific or orphan genes. The <em>Arabidopsis thaliana</em> gene Qua-Quine Starch (<em>QQS</em>) is species specific. Here, we show that altering <em>QQS</em> expression in Arabidopsis affects carbon partitioning to both starch and protein. We hypothesized <em>QQS</em> may be conserved in a feature other than primary sequence, and as such could function to impact composition in another species. To test the potential of <em>QQS</em> in affecting composition in an ectopic species, we introduced <em>QQS</em> into soybean. Soybean T1 lines expressing <em>QQS</em> have up to 80% decreased leaf starch and up to 60% increased leaf protein; T4 generation seeds from field-grown plants contain up to 13% less oil, while protein is increased by up to 18%. These data broaden the concept of <em>QQS</em> as a modulator of carbon and nitrogen allocation, and demonstrate that this species-specific gene can affect the seed composition of an agronomic species thought to have diverged from Arabidopsis 100 million years ago.</p>