WRKY Transcriptional Factor IlWRKY70 from Iris laevigata Enhances Drought and Salinity Tolerances in Nicotiana tabacum

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.

Resolving the Puzzle of Iris maackii (Iridaceae): A Morphological Insight into Its Taxonomy

Since the early 20th century, Iris maackii (Iridaceae) has been considered a synonym of I. laevigata, a synonym of I. pseudacorus, or an accepted species. The current concept of I. maackii in the literature and databases is often applied to yellow-flowered plants with prominently veined rosette leaves, which are diagnostic features of I. pseudacorus growing in Northeast Asia. Therefore, the objective was to clarify the taxonomic identity of I. maackii. This study is based on a critical examination of the literature, on the observed morphological characters in the holotype of I. maackii, and on a morphological comparison of I. maackii with living plants of I. laevigata and I. pseudacorus. Additionally, a morphometric comparison of the seed characters was carried out to clarify the morphological distinction among I. maackii, I. laevigata, and I. pseudacorus. A careful study demonstrated that the rosette leaf texture and the morphology of the flowering stem, fruit, and seeds of I. maackii are identical to or within the variation range of I. laevigata. Thus, I. maackii is morphologically non-distinct from I. laevigata and should be recognized as a taxonomic synonym of the latter. An image of the holotype of I. maackii is provided along with detailed illustrations of I. laevigata and I. pseudacorus.

Comparative analysis of R2R3-MYB transcription factors in the flower of Iris laevigata identifies a novel gene regulating tobacco cold tolerance

Breeding for flower cold resistance is a priority for flower breeding research in northern China. The identification of cold resistance genes will not only provide genetic resources for cold resistance breeding, but also form a basis for the study of plant cold resistance mechanisms. Based on the flower transcriptome of Iris laevigata, 20 R2R3-MYBs were identified and comprehensive analysis, including conservative domain, phylogenetic analyses and functional distribution, were performed for R2R3-MYBs. Expression patterns of the abiotic stress genes under cold stress were detected, the upregulated gene was genetically transformed into tobacco, and the related physiological indicators of the transgenic tobacco were measured. A novel cold resistance gene, IlMYB306, was obtained. qRT-PCR indicated that IlMYB306 was dramatically induced by cold stress and was significantly upregulated in roots. The free proline content, MDA, SOD and POD activity of the transgenic tobacco improved after cold stress, and the chlorophyll content decreased slowly. In addition, overexpression of IlMYB306 improved cold resistance of the seeds. SEM results showed leaves of transgenic tobacco had obvious folds, more grooves and bulges on the lower leaf surface. Overall, we report a novel cold resistance R2R3-MYB gene, IlMYB306, in the flower of I. laevigata, which could improve tobacco cold stress tolerance by thickening the waxy layer, increasing antioxidant activity and the content of proline.