Fig. 3.

MaSAMP protects the healthy citrus trees from CLas infection. (A) The expression level of defense marker genes in the MaSAMP-treated 'Valencia' sweet orange trees was highly induced over a prolonged time course. The relative expression level was analyzed by qRT-PCR and normalized to Actin. (B–E) Two sets of the 'Madam Vinous' sweet orange trees were foliar-sprayed with buffer (mock) or MaSAMP solution (10 μM) before ACP exposure (B) or graft infection (D). The treatment programs for B and D were indicated in a timeline with months (M) at the upper of C and E, respectively. The spray time points (green arrow) and the time when trees died (red star) were indicated. The CLas titer of individual trees in test B and D at the indicated sampling time was shown in the middle of C and E, respectively. The tables of the lower panel of C and E represent the number of the infected and dead trees. (F) MaSAMP was detected with Western blot by anti-MaSAMP antibody in the vascular fluid collected from MaSAMP-sprayed leaves. The midveins were tap-protected before spraying to avoid direct contact of MaSAMP with midveins. (G) Systemic leaves of trees that have lower leaves wiped with MaSAMP solution using a cotton ball were collected at 24 h or 7 d after MaSAMP application. The MaSAMP was detected by Western blot in the vascular fluid of the midvein from systemic untreated leaves. Ponceas staining (PS) was used as the loading control.