Iris lactea var. chinensis (I. lactea var. chinensis) is a perennial herb halophyte with salt and drought tolerance. In this study, full-length transcripts of I. lactea var. chinensis were sequenced using the PacBio RSII sequencing platform. Moreover, the transcriptome was investigated under NaCl or polyethylene glycol (PEG) stress. Approximately 30.89 G subreads were generated and 31,195 unigenes were obtained by clustering the same isoforms by the PacBio RSII platform. A total of 15,466 differentially expressed genes (DEGs) were obtained under the two stresses using the Illumina platform. Among them, 9266 and 8390 DEGs were obtained under high concentrations of NaCl and PEG, respectively. In total, 3897 DEGs with the same expression pattern under the two stresses were obtained. The transcriptome expression profiles of I. lactea var. chinensis under NaCl or PEG stress obtained in this study may provide a resource for the same and different response mechanisms against different types of abiotic stress. Furthermore, the stress-related genes found in this study can provide data for future molecular breeding.

Nitrogen forms (nitrate (NO₃⁻) or ammonium (NH₄⁺)) are vital to plant growth and metabolism. In stevia (Stevia rebaudiana), it is important to assess whether nitrogen forms can influence the synthesis of the high-value terpene metabolites-steviol glycosides (SGs), together with the underlying mechanisms. Field and pot experiments were performed where stevia plants were fertilized with either NO₃⁻ or NH₄⁺ nutrition to the same level of nitrogen. Physiological measurements suggested that nitrogen forms had no significant impact on biomass and the total nitrogen content of stevia leaves, but NO₃⁻-enhanced leaf SGs contents. Transcriptomic analysis identified 397 genes that were differentially expressed (DEGs) between NO₃⁻ and NH₄⁺ treatments. Assessment of the DEGs highlighted the responses in secondary metabolism, particularly in terpenoid metabolism, to nitrogen forms. Further examinations of the expression patterns of SGs synthesis-related genes and potential transcription factors suggested that GGPPS and CPS genes, as well as the WRKY and MYB transcription factors, could be driving N form-regulated SG synthesis. We concluded that NO₃⁻, rather than NH₄⁺, can promote leaf SG synthesis via the NO₃⁻-MYB/WRKY-GGPPS/CPS module. Our study suggests that insights into the molecular mechanism of how SG synthesis can be affected by nitrogen forms.

The family of B-box (BBX) transcription factors contains one or two B-BOX domains and sometimes also features a highly conserved CCT domain, which plays important roles in plant growth, development and stress response. Nevertheless, no systematic study of the BBX gene family in Iris germanica L. has been undertaken. In this study, a set of six BBX TF family genes from I. germanica was identified based on transcriptomic sequences, and clustered into three clades according to phylogenetic analysis. A transient expression analysis revealed that all six BBX proteins were localized in the nucleus. A yeast one-hybrid assay demonstrated that IgBBX3 has transactivational activity, while IgBBX1, IgBBX2, IgBBX4, and IgBBX5 have no transcriptional activation ability. The transcript abundance of IgBBXs in different tissues was divided into two major groups. The expression of IgBBX1, IgBBX2, IgBBX3 and IgBBX5 was higher in leaves, whereas IgBBX4 and IgBBX6 was higher in roots. The stress response patterns of six IgBBX were detected under phytohormone treatments and abiotic stresses. The results of this study lay the basis for further research on the functions of BBX gene family members in plant hormone and stress responses, which will promote their application in I. germanica breeding.

Cadmium (Cd) stress has a major impact on ecosystems, so it is important to find suitable Cd-tolerant plants while elucidating the responsible molecular mechanism for phytoremediation to manage Cd soil contamination. Iris lactea var. chinensis is an ornamental perennial groundcover plant with strong tolerance to Cd. Previous studies found that IlAP2, an AP2/ERF superfamily gene, may be an interacting partner of the metallothionein gene IlMT2a, which plays a key role in Cd tolerance. To study the role of IlAP2 in regulating Cd tolerance in I. lactea, we analyzed its regulation function and mechanism based on a yeast two-hybrid assay, a bimolecular fluorescence complementation test, quantitative real-time PCR, transgenics and transcriptome sequencing. The results showed that IlAP2 interacts with IlMT2a and may cooperate with other transcription factors to regulate genes involved in signal transduction and plant hormones, leading to reduced Cd toxicity by hindering Cd transport. These findings provide insights into the mechanism of IlAP2-mediated stress responses to Cd and important gene resources for improving plant stress tolerance in phytoremediation.