Transcriptomic and metabolic studies on the role of inorganic and organic iodine compounds in lettuce plants.

Iodine (I) is considered a beneficial element or even micronutrient for plants. The aim of this study was to determine the molecular and physiological processes of uptake, transport, and metabolism of I applied to lettuce plants. KIO3, KIO3 + salicylic acid, 5-iodosalicylic acid and 3,5-diiodosalicylic acid were applied. RNA-sequencing was executed using 18 cDNA libraries constructed separately for leaves and roots from KIO3, SA and control plants. De novo transcriptome assembly generated 1937.76 million sequence reads resulting in 27,163 transcripts with N50 of 1638 bp. 329 differentially expressed genes (DEGs) in roots were detected after application of KIO3, out of which 252 genes were up-regulated, and 77 were down-regulated. In leaves, 9 genes revealed differential expression pattern. DEGs analysis indicated its involvement in such metabolic pathways and processes as: chloride transmembrane transport, phenylpropanoid metabolism, positive regulation of defense response and leaf abscission, and also ubiquinone and other terpenoid-quinone biosynthesis, protein processing in endoplasmic reticulum, circadian rhythm including flowering induction as well as a putative PDTHA (i.e. Plant Derived Thyroid Hormone Analogs) metabolic pathway. qRT-PCR of selected genes suggested their participation in the transport and metabolism of iodine compounds, biosynthesis of primary and secondary metabolites, PDTHA pathway and flowering induction.

Transcriptome Dynamics Underlying Planticine®-Induced Defense Responses of Tomato (Solanum lycopersicum L.) to Biotic Stresses.

The induction of natural defense mechanisms in plants is considered to be one of the most important strategies used in integrated pest management (IPM). Plant immune inducers could reduce the use of chemicals for plant protection and their harmful impacts on the environment. Planticine® is a natural plant defense biostimulant based on oligomers of α(1→4)-linked D-galacturonic acids, which are biodegradable and nontoxic. The aim of this study was to define the molecular basis of Planticine's biological activity and the efficacy of its use as a natural plant resistance inducer in greenhouse conditions. Three independent experiments with foliar application of Planticine® were carried out. The first experiment in a climatic chamber (control environment, no pest pressure) subjected the leaves to RNA-seq analysis, and the second and third experiments in greenhouse conditions focused on efficacy after a pest infestation. The result was the RNA sequencing of six transcriptome libraries of tomatoes treated with Planticine® and untreated plants; a total of 3089 genes were found to be differentially expressed genes (DEGs); among them, 1760 and 1329 were up-regulated and down-regulated, respectively. DEG analysis indicated its involvement in such metabolic pathways and processes as plant-pathogen interaction, plant hormone signal transduction, MAPK signaling pathway, photosynthesis, and regulation of transcription. We detected up-regulated gene-encoded elicitor and effector recognition receptors (ELRR and ERR), mitogen-activated protein kinase (MAPKs) genes, and transcription factors (TFs), i.e., WRKY, ERF, MYB, NAC, bZIP, pathogenesis-related proteins (PRPs), and resistance-related metabolite (RRMs) genes. In the greenhouse trials, foliar application of Planticine® proved to be effective in reducing the infestation of tomato leaves by the biotrophic pathogen powdery mildew and in reducing feeding by thrips, which are insect herbivores. Prophylactic and intervention use of Planticine® at low infestation levels allows the activation of plant defense mechanisms.