Figure 4.

nf2100 produces senescent nodules with higher immunity stimulation than the other senescence mutants. A, Expression analysis of PRs and CPs in 21-dpi nodules of WT or nf2100 cultivated in vitro shows the upregulation of these genes in nf2100. B, Cultivation of nf2100 or the WT on sand/perlite led to the increase of PR expression and reduction of CP expression in 24-dpi nodules of nf2100 compared to the WT. Values in (A) and (B) represent the mean of induction folds in the tested mutants compared to the WT. The RT-qPCR analyses in (A) and (B) were made on three biological repetitions with two technical replicates. For each experiment, 16 and 5 plants were analyzed for, respectively, in vitro and sand/perlite conditions. The actin housekeeping gene was used for the expression normalization. Error bars indicate se and the asterisks represent significant variations (P < 2.5%) compared to the WT using Mann–Whitney statistical test. C, Analysis of 21-dpi in vitro nodules induced by S. medicae WSM419 lacZ reveals that nf2100 produces nodules with few necrotic cells. D, In contrast, sand/perlite cultivation leads to the apparition of a large necrotic area. The arrow shows necrotic cells and the scale bars in (C) and (D) represent 500 µm.