Drought and high salinity greatly affect plant growth and development. WRKY transcription factors play a key role in plant tolerance to abiotic stress, but the functions of WRKYs in the ornamental monocotyledon Iris laevigata remain largely unexplored. In this study, we cloned IlWRKY70 and found that it is a Group III WRKY localized in the nucleus. The expression of IlWRKY70 was induced by NaCl and PEG-6000, which reached peaks (4.38 and 5.65 times) after 3 h and 1 h, respectively. The exogenous overexpression of IlWRKY70 in N. tabacum significantly improved the resistance under NaCl and drought treatments, as evidenced by higher germination rates, longer root lengths, and increased fresh weights compared to those of control plants. In addition, transgenic seedlings showed significantly reduced wilting, higher photosynthetic performance, higher Fv/Fm and chlorophyll content, and lower stomatal conductance. Moreover, transgenic lines showed higher antioxidant enzymatic activities, lower reactive oxygen species (ROS), and lower malondialdehyde contents. Accordingly, we also found higher expressions of antioxidant defense genes, including SOD, CAT, and POD, in transgenic lines compared to controls under salt and drought stresses. Thus, IlWRKY70 enhances the abilities of salt and drought tolerances in plants, at least partially, via ROS regulation and can be used for breeding I. laevigata possessing enhanced salt and drought resistances.

Iris laevigata is an ornamental plant and so its wild genetic resources need to be protected. However, traditional inefficient propagation limits its landscape applications. In this study, we assessed the effects of phytohormones on growth of I. laevigata at various culture stages using roots and hypocotyls as explants and established an efficient micropropagation system. The highest callus induction of hypocotyl (75.0%) was obtained using Murashige and Skoog medium containing 6-benzylaminopurine (6-BA), 0.5 mg L⁻¹ + 2,4-dichlorophenoxyacetic acid (2,4-D), 1.0 mg L⁻¹ + 1-naphthylacetic acid (NAA), and 0.4 mg L⁻¹. Similarly, the highest callus induction (73.3%) of roots was achieved with 6-BA 0.5 mg L⁻¹ + 2,4-D 0.5 mg L⁻¹ + NAA 0.4 mg L⁻¹. The calli induced from hypocotyl and root tissues achieved 39.7% and 49.5% adventitious shoot induction on a medium containing indole-3-butyric acid (IBA) 0.5 mg L⁻¹ + 6-BA 1.5 mg L⁻¹ + NAA 1.0 mg L⁻¹ and 6-BA 2.0 mg L⁻¹ + NAA 0.4 mg L⁻¹ + kinetin (KT) 1.0 mg L⁻¹, respectively. The rooting of adventitious shoots reached 93.3% in the medium supplemented with NAA 0.2 mg L⁻¹. The survival of regenerated plants reached 90.0% after being transplanted into soil. This study provides an efficient and reliable propagation method for I. laevigata for landscape applications and the preservation of wild genetic material.

Iris sanguinea features upright, stiff leaves, making it an excellent cut-foliage material, with its tall leaf architecture greatly enhancing ornamental value in landscaping. However, during the leaf expansion phase, plants frequently exhibit loose foliage arrangement, excessive spreading, and compromised mechanical strength, culminating in lodging and a concomitant decline in ornamental quality. Plant height in I. sanguinea is strongly regulated by phytohormones. This study showed that exogenous GA at concentrations of 50 mg·L⁻¹, 100 mg·L⁻¹, and 200 mg·L⁻¹ increased seedling height by 5.7%, 8.8%, and 12.7%, respectively, through foliar spraying on I. sanguinea seedlings grown ex vitro in a greenhouse; conversely, PAC treatment at equivalent concentrations suppressed growth by 19.3%, 21.0%, and 22.2%, respectively. Two pivotal GA signaling components, GAI and GID1a, were isolated from I. sanguinea. Subcellular localization confirmed that both IsGAI and IsGID1a proteins localize to the nucleus. Overexpression vectors pCAMBIA1300-IsGAI-GFP and pCAMBIA1300-IsGID1a-GFP were constructed and expressed in Arabidopsis thaliana. Transgenic lines overexpressing IsGAI showed significantly reduced plant height, hypocotyl elongation, and bolting, whereas IsGID1a overexpression promoted these traits. Exogenous GA application partially reversed the dwarf phenotype induced by IsGAI overexpression and further potentiated the height enhancement observed in IsGID1a-overexpressing lines. This study identifies two key genes controlling plant height and provides a theoretical basis and genetic resources for precisely engineering plant architecture in I. sanguinea. This is especially important for developing dwarf varieties with enhanced ornamental and agronomic traits, offering significant potential in the landscaping and cut flower industries.