3.5 NtLOX5 and NtLOX6 inhibit the accumulation of FA in tobacco seeds
Among the four direct targets of NtMYB12a, the homologous gene ofNtSFAR4 has been shown to be involved in FA degradation in Arabidopsis (Huang et al., 2015). TheNtLOX5 and NtLOX6 genes encode 9-LOX and 13-LOX proteins (Figure 8a), respectively. To determine whether they affect FA content in tobacco, the overexpression and RNAi plants of these two genes were generated. As shown in Figure 8b & 8c, the transcription levels ofNtLOX5 and NtLOX6 genes significantly increased in their OE lines, but significantly decreased in their RNAi lines, respectively. The FA contents in the mature seeds of two independent NtLOX5-OElines were significantly lower than those in the WT seeds, but the FA contents in the seeds of three NtLOX5-RNAi lines were all significantly higher than those in the WT seeds (Figure 8d). The percentage of PUFA (18:2 and 18:3) in the WT seeds was about 77%, which significantly decreased to 67%-71% in the three independentNtLOX5-OE lines, but significantly increased to 81% and 84% in two independent NtLOX5-RNAi lines (Figure 8e). Similarly, the FA contents in the mature seeds of three independent NtLOX6-OE lines were significantly lower than those in the WT seeds, but the FA contents in the seeds of three NtLOX6-RNAi lines were all significantly higher than those in the WT seeds (Figure 8f). The percentage of PUFA significantly decreased to 69%-72% in the three independentNtLOX6-OE lines, but significantly increased to 83% and 84% in two NtLOX6-RNAi lines (Figure 8g). Taken together, the activation of NtLOX5 and NtLOX6 could significantly inhibit the accumulation of FA in tobacco seeds.