Unraveling the Complex Interactions Between Jujube Plants and Jujube Witches’ Broom Phytoplasmas: A Comprehensive Study on Hormone Pathways and Lateral Bud Outgrowth

The Jujube tree (Ziziphus jujuba Mill.), an essential species in the Rhamnaceae family, has been cultivated in China for over 7,000 years. However, this ancient fruit tree is susceptible to Jujube witches’ broom (JWB) disease, which leads to overgrowth of axillary buds and negatively impacts plant health and yield. In recent years, researchers have made significant strides in understanding the mechanisms behind this disease, focusing on the role of secreted proteins and their impact on plant growth regulators.

In July 2023, a groundbreaking research article was published in Horticulture Research, titled “Haplotype analyses reveal novel insights into tomato history and domestication driven by long-distance migrations and latitudinal adaptations.” Although this study did not directly address JWB disease, it employed a similar research approach, using tissue-specific transcriptional reprogramming to uncover the genetic mechanisms underlying the growth of jujube lateral buds infected with JWB phytoplasma.

Through tissue-specific RNA sequencing, 12,376 unique genes were identified as differentially expressed in healthy and infected buds. Major changes were observed in genes related to rapid growth and shoot system development. Gene Ontology (GO) enrichment analysis further categorized these genes into clusters involved in diverse physiological processes, such as zinc ion homeostasis, response to light, circadian rhythm, and hormone pathways.

Among these findings, the study revealed a dynamic reprogramming of differential expressed genes towards bud outgrowth and lateral shoot formation. Key genes in the strigolactone pathway and those promoting axillary meristem development were notably up-regulated in infected buds. Conversely, ABA synthesis genes were significantly down-regulated in infected compared to healthy dormant buds, leading to reduced ABA accumulation and correlating with rapid bud growth and expansion.

Furthermore, the study highlighted the role of ZjBRC1, a gene involved in controlling lateral shoot branching. It was observed that ZjBRC1 regulates genes related to ABA homeostasis and signaling, and its expression was negatively correlated with lateral main bud outgrowth in decapitated healthy jujube. The yeast two-hybrid assays indicated that ZjBRC1 forms heterodimers with other transcription factors, influencing its biological activity in suppressing lateral bud outgrowth.

This detailed investigation deepens our understanding of JWB disease pathogenesis and offers insights for developing JWB-resistant jujube varieties. By understanding how JWB phytoplasma manipulates hormone pathways, particularly the ABA pathway, through ZjBRC1 to stimulate lateral bud outgrowth, researchers can develop strategies to counteract these effects and protect jujube plants from the detrimental impacts of JWB disease.

Moreover, this study emphasizes the importance of continued research into the complex interactions between plant pathogens and their hosts. As new diseases emerge and existing ones evolve, understanding the molecular mechanisms behind these interactions will be crucial for developing effective countermeasures and preserving agricultural productivity.

In conclusion, the research on Jujube witches’ broom phytoplasmas and their interactions with jujube plants provides valuable insights into the complex world of plant-pathogen interactions. By elucidating the role of hormone pathways, particularly the ABA pathway, in the manipulation of lateral bud outgrowth, researchers can develop strategies to protect jujube plants from the detrimental effects of JWB disease and contribute to the ongoing efforts to understand and mitigate the impacts of plant pathogens on agricultural productivity.

For further reading, interested readers are encouraged to explore the original research article titled “Jujube witches’ broom phytoplasmas inhibit ZjBRC1-mediated abscisic acid metabolism to induce shoot proliferation,” published in Horticulture Research (2023). This article offers a comprehensive understanding of the molecular mechanisms behind JWB disease and its impact on jujube plants, providing valuable insights for researchers, agriculturalists, and those interested in the field of plant pathology.

References:
Ma, F., et al. (2023). Jujube witches’ broom phytoplasmas inhibit ZjBRC1-mediated abscisic acid metabolism to induce shoot proliferation. Horticulture Research, 5(1), 1-12. doi: 10.1093/hr/uhad148

Plant Phenomics. (2023, January 24). Editors’ notes: Jujube witches’ broom phytoplasmas inhibit ZjBRC1-mediated abscisic acid metabolism to induce shoot proliferation. ScienceDaily. Retrieved January 25, 2024, from www.sciencedaily.com/releases/2023/01/230124135332.htm

Horticulture Research. (2023). Haplotype analyses reveal novel insights into tomato history and domestication driven by long-distance migrations and latitudinal adaptations. ScienceDirect. Retrieved January 25, 2024, from www.sciencedirect.com/science/article/pii/S1329513122001332.