Abstract:
Objective Changes in the cell structure and gene expression of leaf caused by the pathogenesis of lily upper leaf necrosis (ULN) were studied to understand the molecular mechanism of the disease on Oriental Lily Tarrango (Lilium tarrango) .
Methods Ultrastructure of the leaves from normal as well as mildly and severely ULN-infected lily plants was examined under a scanning electron microscope (SEM) and a projection electron microscope (TEM). Transcriptome sequences of the leaf specimens with or without calcium spraying were compared to identify the differentially expressed genes.
Result The size of epidermal cells on the adaxial leaf surface shrank as the ULN worsened with vacuolar water loss. A total of 7 185 differentially expressed genes were identified that included 5 860 specific and 1 325 common differentially expressed genes. The KEGG enrichment analysis showed that the genes were enriched in the metabolic pathways, pyruvate metabolism, biosynthesis of secondary metabolites, and carbon fixation of photosynthetic organisms in all 4 groups of specimens with or without calcium spraying. FOLK, PLD1_2, ATPeF1B, KCS, CALM, ENO, and pel were significantly downregulated during the progress of ULN on the leaves. After the calcium spraying, CALM, CPK, EIN2, AUX1, PLD1_2, and SORD were upregulated.
Conclusion Calcium deficiency was deemed to be the key factor that led to ULN on the lily plants. The deficiency produced the symptoms, such as vacuolar moisture loss and cellular shrinkage, might be regulated by the hormone metabolisms related to abscisic acid, ethylene, and auxin.
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