Physiological and transcriptomic responses of two Artemisia californica populations to drought: implications for restoring drought-resilient native communities

As climate change brings drier and more variable rainfall patterns to many arid and semi-arid regions, land managers must re-assemble appropriate plant communities for these conditions. Transcriptome sequencing can elucidate the molecular mechanisms underlying plant responses to changing environmental conditions, potentially enhancing our ability to screen suitable genotypes and species for restoration. We examined physiological and morphological traits and transcriptome sequences of coastal and inland populations of California sagebrush (Artemisia californica), a critical shrub used to restore coastal sage scrub vegetation communities, grown under low and high rainfall environments. The populations are located approximately 36 km apart but differ in mean annual precipitation, with the coastal population experiencing approximately 42% more rainfall. We found subtle phenotypic differences between populations, with plants from the coastal population showing higher rates of carbon assimilation and growth, and a more considerable decrease in function in response to drought compared to the inland population. We observed more extensive transcriptome responses in A. californica root compared to leaf tissues. While the two populations shared several responses to drought, such as upregulated protein folding and stabilization, coastal populations demonstrated more extensive responses to stress than inland populations. Furthermore, transcriptomic results from inland populations showed reduced aboveground growth and early flowering which may reduce evaporative loss and maximize reproductive output, respectively, under low rainfall conditions. These patterns are consistent with a trade-off between growth and stress tolerance, where the coastal population has a strategy more aligned with growth compared to the inland population, which may be better able to tolerate stress. Identifying drought-tolerant populations can ultimately lead to cost savings in maintaining restored areas under future climate conditions.