Transcriptome Mechanisms of Tomato Seedlings Induced by Low-Red to Far-Red Light Ratio under Calcium Nitrate Stress

In recent times, the excessive accumulation of nitrate has been one of the main reasons for the secondary salinization of greenhouse soils. Light plays a key role in a plant's growth, development, and response to stress. A low-red to far-red (R:FR) light ratio could enhance plant salinity tolerance, but the mechanism at a molecular level is unclear. Thus, we analyzed the transcriptome responses of tomato seedlings to calcium nitrate stress under either a low R:FR ratio (0.7) or normal light conditions. Under calcium nitrate stress, a low R:FR ratio enhanced both the antioxidant defense system and the rapid physiological accumulation of proline in tomato leaves, which promoted plant adaptability. Using weighted gene co-expression network analysis (WGCNA), three modules including 368 differentially expressed genes (DEGs) were determined to be significantly associated with these plant traits. Functional annotations showed that the responses of these DEGs to a low R:FR ratio under excessive nitrate stress were enriched in the areas of hormone signal transduction, amino acid biosynthesis, sulfide metabolism, and oxidoreductase activity. Furthermore, we identified important novel hub genes encoding certain proteins, including FBNs, SULTRs, and GATA-like transcription factor, which may play a vital role in low R:FR light-induced salt responses. These findings offer a new perspective on the mechanisms and environmental implications behind low R:FR ratio light-modulated tomato saline tolerance.

Automated summary

In recent times, excessive nitrate accumulation has led to secondary salinization of greenhouse soils. A low red to far-red (R:FR) light ratio can enhance tomato plant salinity tolerance, but its molecular mechanism is unclear. Transcriptome analysis of tomato seedlings exposed to calcium nitrate stress under low R:FR ratio or normal light conditions revealed that a low R:FR ratio promotes antioxidant defense and proline accumulation, improving plant adaptability. Differentially expressed genes associated with hormone signal transduction, amino acid biosynthesis, sulfide metabolism, and oxidoreductase activity were identified. Novel hub genes encoding proteins like FBNs, SULTRs, and GATA-like transcription factors were also discovered, highlighting their role in low R:FR light-induced salt responses. These findings provide new insights into the mechanisms and environmental implications of low R:FR ratio light-modulated tomato saline tolerance.