Jujube witches' broom phytoplasmas inhibit ZjBRC1-mediated abscisic acid metabolism to induce shoot proliferation.

Jujube witches' broom (JWB) phytoplasmas parasitize the sieve tubes of diseased phloem and cause an excessive proliferation of axillary shoots from dormant lateral buds to favour their transmission. In previous research, two JWB effectors, SJP1 and SJP2, were identified to induce lateral bud outgrowth by disrupting ZjBRC1-mediated auxin flux. However, the pathogenesis of JWB disease remains largely unknown. Here, tissue-specific transcriptional reprogramming was examined to gain insight into the genetic mechanisms acting inside jujube lateral buds under JWB phytoplasma infection. JWB phytoplasmas modulated a series of plant signalling networks involved in lateral bud development and defence, including auxin, abscisic acid (ABA), ethylene, jasmonic acid, and salicylic acid. JWB-induced bud outgrowth was accompanied by downregulation of ABA synthesis within lateral buds. ABA application rescued the bushy appearances of transgenic overexpressing and in Col-0 and in the mutant. Furthermore, the expression of and ABA-related genes and was negatively correlated with lateral main bud outgrowth in decapitated healthy jujube. Molecular evidence showed that ZjBRC1 interacted with ZjBRC2 via its N-terminus to activate and expression and ABA accumulation in transgenic jujube calli. In addition, widely regulated differentially expressed genes related to ABA homeostasis and ABA signalling, especially by binding to and suppressing ABA receptors. Therefore, these results suggest that JWB phytoplasmas hijack the -mediated ABA pathways to stimulate lateral bud outgrowth and expansion, providing a strategy to engineer plants resistant to JWB phytoplasma disease and regulate woody plant architecture to promote crop yield and quality.