Adaptional evolution of trichome in <i>Caragana korshinskii</i> to natural drought stress on the Loess Plateau, China

Abstract

<i>Caragana korshinskii</i> is commonly employed to improve drought ecosystems on the Loess Plateau, although the molecular mechanism at work is poorly understood, particularly in terms of the plant's ability to tolerate drought stress. Water is the most severe limiting factor for plant growth on the Loess Plateau. The trichome is known to play an efficient role in reducing water loss through decreasing the rate of transpiration, so in this study, we focused on the trichome-related gene expression of ecological adaptation in <i>C. korshinskii</i> under low precipitation conditions. In order to explore the responses of trichomes to drought, we selected two experimental sites from wet to dry along the Loess Plateau latitude gradient for observation. Micro-phenomena through which trichomes grew denser and larger under reduced precipitation were observed using a scanning electron microscope; <i>de novo</i> transcriptomes and quantitative PCR were then used to explore and verify gene expression patterns of <i>C. korshinskii</i> trichomes. Results showed that <i>GIS2</i>,<i>TTG1</i>, and <i>GL2</i> were upregulated (as key positive-regulated genes on trichome development), while <i>CPC</i> was downregulated (negative-regulated gene). Taken together, our data indicate that downstream genes of gibberellin and cytokinin signaling pathways, alongside several cytoskeleton-related genes, contribute to modulating trichome development to enhance transpiration resistance ability and increase the resistance to drought stress in <i>C. korshinskii</i>.