Abstract
The plasma seed treatment is effective for promoting seed germination in many crops. However, the biological mechanism remains unclear. Therefore, mRNA sequencing was used to screen differentially expressed genes in the germination process of Andrographis paniculata seeds treated with air plasma (power density = 8.99 J/cm3). Following plasma treatment, the germination percentages were significantly higher than those of the control, they were 3.5±0.6% vs. 0 at 28 hours after sowing (HAS) and 50.3±2.6% vs. 37.3±1.7% at 48 HAS. After unigenes were assembled and annotated, 125 differentially expressed genes (DEGs) were detected at 28 HAS, compared with nine DEGs at 48 HAS, but no DEGs were detected at 0 HAS, indicating that air plasma treatment mainly changed the gene expression of A. paniculata seeds at 28 HAS. The NCED5 expression level of the treated group was less than one-fifth of the control, and the expressions of three ethylene response factors were significantly higher than the control at 28 HAS, indicating that lower abscisic acid levels play an important role and ethylene signal transduction also participates in radicle protrusion. ACO, NRT1 and PRP3 expressions were significantly higher than in the control at 48 HAS, suggesting that higher ethylene levels cause the endosperm cap to weaken and start to grow root hairs and lateral roots earlier. These findings reveal that plasma promotes seed germination mainly by regulating the expression of hormone-related genes. And the possible signal transduction of related hormones was discussed.
Highlights
Seed germination is a crucial event in the life cycle of seed plants
Short-term (3 s) air plasma treatment of A. paniculata seeds altered the gene expression during germination, with the major changes occurring in the late germination stage (125 differentially expressed genes (DEGs) at 28 hours after sowing (HAS)), followed by the post-germination stage (9 DEGs at 48 HAS)
Studies showed that RNS promoted abscisic acid (ABA) degradation by activating the CYP707A gene and promoted gibberellic acid https://doi.org/10.1371/journal.pone.0240939.g005 (GA) synthesis by activating GA3ox, promoting seed germination [45, 46]
Summary
Seed germination is a crucial event in the life cycle of seed plants. Under natural conditions, there is heterogeneity in the germination duration of seed populations within the same species [1, 2]. A previous study showed that after air plasma seed treatment, germination and seedling emergence, and light sensitivity of Paulownia tomentosa seeds was improved [14]. Seed germination is the integrated process of a series of complex physiological and biochemical metabolic reactions involving a series of gene expressions and the signal transductions of many molecules. Nakano et al [19] used DNA microarray analysis to study the changes of polygene expressions responding to plasma seed treatment In this investigation, RNA-seq was used to screen differentially expressed genes in the germination process of A. paniculata seeds treated with air plasma. The biological mechanism of seed germination promotion by plasma may be revealed so as to provide a biological basis for the application of plasma technology in seed processing
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