Phenylalanine ammonia-lyase (PAL, E.C.4.3.1.5) catalyzes the benzene propane metabolism and is the most extensively studied enzyme of the phenylpropanoid pathway. However, the role of PAL genes in Astragalus membranaceus, a non-model plant showing high capability toward abiotic stress, is less studied. Here, we cloned AmPAL and found that it encodes a protein that resides in the cytoplasmic membrane. The mRNA of AmPAL was strongly induced by NaCl or NaHCO₃ treatment, especially in the root. Overexpressing AmPAL in Nicotiana tabacum resulted in higher PAL enzyme activities, lower levels of malondialdehyde (MDA), and better root elongation in the seedlings under stress treatment compared to the control plants. The protective role of AmPAL under saline-alkali stress was also observed in 30-day soil-grown plants, which showed higher levels of superoxide dismutase (SOD), proline, and chlorophyll compared to wild-type N. Tabacum. Collectively, we provide evidence that AmPAL is responsive to multiple abiotic stresses and that manipulating the expression of AmPAL can be used to increase the tolerance to adverse environmental factors in plants.

Iris laevigata Fisch. is an excellent ornamental plant in cold regions due to its unique ornamental ability and strong cold resistance. However, the flowering period of the population is only about 20 days, greatly limiting its potential uses in landscaping and the cutting flower industry. In addition, I. laevigata is often challenged with various abiotic stresses including high salinity and drought in its native habitats. Thus, breeding novel cultivars with delayed flowering time and higher resistance to abiotic stress is of high importance. In this study, we utilized sequencing data from the I. laevigata transcriptome to identify WRKYs and characterized IlWRKY22, a key transcription factor that modulates flowering time and abiotic stress responses. IlWRKY22 is induced by salt and drought stress. We cloned IlWRKY22 and found that it is a Group IIe WRKY localized in the nucleus. Overexpressing IlWRKY22 in Arabidopsis thaliana (L.) Heynh. and Nicotiana tabacum L. resulted in a delayed flowering time in the transgenic plants. We created transgenic N. tabacum overexpressing IlWRKY22, which showed significantly improved resistance to both salt and drought compared to the control plants. Thus, our study revealed a unique dual function of IlWRKY22, an excellent candidate gene for breeding novel Iris cultivars of desirable traits.

Iris laevigata is ideal for gardening and landscaping in northeast China because of its beautiful flowers and strong cold resistance. However, the short length of flowering time (2 days for individual flowers) greatly limits its applications. Molecular breeding and engineering hold high potential for producing I. laevigata of desirable flowering properties. A prerequisite is to identify and characterize key flowering control genes, the identity of which remains largely unknown in I. laevigata due to the lack of genome information. To fill this knowledge gap, we used sequencing data of the I. laevigata transcriptome to identify MADS-box gene-encoding transcription factors that have been shown to play key roles in developmental processes, including flowering. Our data revealed 41 putative MADS-box genes, which consisted of 8 type I (5 Mα and 3 Mβ, respectively) and 33 type II members (2 MIKC* and 31 MIKC^C, respectively). We then selected IlSEP3 and IlSVP for functional studies and found that both are localized to the nucleus and that they interact physically in vitro. Ectopic expression of IlSEP3 in Arabidopsis resulted in early flowering (32 days) compared to that of control plants (36 days), which could be mediated by modulating the expression of FT, SOC1, AP1, SVP, SPL3, VRN1, and GA20OX. By contrast, plants overexpressing IlSVP were phenotypically similar to that of wild type. Our functional validation of IlSEP3 was consistent with the notion that SEP3 promotes flowering in multiple plant species and indicated that IlSEP3 regulates flowering in I. laevigata. Taken together, this work provided a systematic identification of MADS-box genes in I. laevigata and demonstrated that the flowering time of I. laevigata can be genetically controlled by altering the expression of key MADS-box genes.

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.

Drought and salinity are critical abiotic stresses that constrain plant growth. Although MYB transcription factors mediate plant responses to abiotic stresses, their functions in the monocot I. laevigata remain unexplored. Here, we identified a nuclear-localized gene, IlMYB108, which was rapidly upregulated under NaCl and PEG-6000 treatments. Overexpression of IlMYB108 in tobacco enhanced root growth under salt and drought conditions. At the seedling stage, transgenic lines maintained higher leaf growth rates and plant height with reduced wilting during 14 days of continuous stress. Physiologically, transgenic plants exhibited a higher net photosynthetic rate (Pn), maximum photochemical efficiency of photosystem II (Fv/Fm), and chlorophyll content, alongside lower stomatal conductance (Gs), intercellular CO₂ concentration (Ci), and transpiration rate (Tr). They also accumulated less malondialdehyde (MDA), superoxide anion (O₂⁻), and hydrogen peroxide (H₂O₂), which was attributed to enhanced activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), as confirmed by p-Nitro-Blue tetrazolium chloride (NBT) and 3,3′-diaminobenzidine tetrahydrochloride (DAB) staining. Moreover, IlMYB108 up-regulated stress-responsive and antioxidant genes. Collectively, IlMYB108 functions as a key gene that enhances tobacco tolerance to salt and drought stress by coordinating root development, photosynthetic efficiency, water balance and antioxidant defense, thereby providing a valuable genetic resource for breeding stress-resilient plants.

"‘Donglin Ziyun’: A New Iris Sanguinea Cultivar" published on Jun 2025 by American Society for Horticultural Science.