Expression profiles of transcription factors and aquaporins suggest putative roles in rubber biosynthesis regulation and drought stress adaptation in guayule

In arid regions of the southwestern United States, selecting drought-tolerant crops is essential for sustaining agricultural productivity and resource efficiency. Guayule (Parthenium argentatum Gray), a desert rubber-producing plant, utilizes complex mechanisms to adapt to water-limited environments. Understanding these strategies is important for enhancing drought resilience and maximizing rubber production. This study investigated guayule’s transcriptional response to drought stress in two developed cultivars, AZ-4 and CAL-2, selected for their contrasting responses to reduced irrigation. RNA sequencing and bioinformatics analyses revealed key transcription factors governing metabolic and stress-response pathways, highlighting distinct regulatory strategies. As indicated by GO-term enrichment and KEGG pathway analyses, under drought stress conditions, AZ-4 exhibited a more dynamic regulatory approach with more transcripts differentially regulated, emphasizing resource management and adaptive stress-response mechanisms. In contrast, CAL-2 maintained stability through precise regulatory adjustments and external defense strategies. The two cultivars demonstrated core stress-response mechanisms, particularly regulating AP2/ERF, MYB, and NAC transcription factor families for downstream regulations. Furthermore, both cultivars utilized the regulation of six key families, including AP2/ERF, bHLH, bZIP, MYB, NAC, and WRKY, that govern the MEP (methylerythritol phosphate) and MVA (mevalonate) pathways for terpenoid and natural rubber biosynthesis. However, AZ-4 displayed stronger baseline regulation of rubber biosynthesis under non-stress conditions. Additionally, aquaporin expression patterns suggested selective upregulation of PIP1-2, PIP1-4, and NIP5-1, as a compensatory mechanism for maintaining physiological functions under drought stress. These findings enhance our understanding of guayule’s drought tolerance and rubber production potential. Building on this foundation, future research should further investigate the molecular drivers of drought adaptation, leveraging multi-omics approaches to refine cultivar selection and optimize rubber yield under water-limited conditions, ultimately offering valuable help for breeding and genetic engineering strategies to improve crop performance in arid regions of the southwestern United States.