Unraveling morphological, physiological, and transcriptomic alterations underlying the formation of little leaves in phytoplasma-infected sweet cherry trees

Authors: TAN, YUE - Shangdong Institute Of Pomology; XU, LI - Shangdong Institute Of Pomology; ZHU, MIN - Shangdong Institute Of Pomology; Zhao, Yan; WEI, HAIRONG - Shangdong Institute Of Pomology; Wei, Wei

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2024
Publication Date: 9/18/2024
Citation: Tan, Y., Xu, L., Zhu, M., Zhao, Y., Wei, H., Wei, W. 2024. Unraveling morphological, physiological, and transcriptomic alterations underlying the formation of little leaves in phytoplasma-infected sweet cherry trees. Plant Disease. https://doi.org/10.1094/PDIS-04-24-0862-RE.
DOI: https://doi.org/10.1094/PDIS-04-24-0862-RE

Interpretive Summary: Phytoplasmas are small plant pathogens that induce various symptoms in different plant species, including witches'-broom (WB), characterized by densely packed small leaves. However, the specific mechanism driving the little leaf formation remains unclear. In this study, scientists from ARS and their collaborators investigated the impact of phytoplasma infection on sweet cherry trees, with a particular focus on the development of small leaves within WB structures and the underlying molecular and cellular processes. The study employed morphological, physiological, and transcriptomic analyses to assess the effects of phytoplasma infection. The results uncovered indications of premature leaf senescence, disturbances in sugar metabolism and hormone levels, as well as impaired ribosome biogenesis, all contributing to the formation of little leaves. Furthermore, the upregulation of marker genes associated with premature leaf senescence shed light on the intricate interplay between leaf development and pathogen-induced stress responses. Overall, this study provides valuable insights into the molecular mechanisms of little leaf formation and offers potential strategies for managing phytoplasma diseases in sweet cherry cultivation. This article holds promise for scientists and students interested in pathogen-induced plant stress, pathogen-host interactions, and high-throughput omics studies.

Technical Abstract: Phytoplasmas are a group of minute and intracellular bacteria that can infect a wide range of plant species. At later infection stages, phytoplasmas induce excessive vegetative growth, known as witches'-broom (WB). The WB structure is composed of densely packed little leaves and is often accompanied by chlorosis (yellowing). However, the underlying mechanisms behind the formation of these little leaves within the WB structure remained elusive. The present study utilized morphological, physiological, and transcriptomic analyses to examine the underlying molecular and cellular events that occurred during little leaf formation in sweet cherry trees infected with sweet cherry virescence (SCV) phytoplasma. Morphological and microstructural examinations unveiled distinct signs of premature leaf senescence, including reductions in leaf size, chlorosis, and alterations in leaf shape. Physiological assessments revealed disruptions in sugar metabolism and changes in hormone levels. Furthermore, transcriptomic analysis uncovered impaired ribosome biogenesis, a crucial process that is essential for protein synthesis, cell growth, and leaf development. Disruptions in ribosome biogenesis impeded cell cycle progression, thus affecting plant morphogenesis. Moreover, the upregulation of marker genes associated with premature leaf senescence further highlights the complex interactions between leaf development, premature leaf senescence, and pathogen-induced stress responses in sweet cherry trees infected with phytoplasma. The findings not only shed light on complicated molecular mechanisms of little leaf formation but also offer valuable insights into the dynamics of plant-pathogen interactions. This knowledge may provide insights into developing effective strategies for managing phytoplasma diseases in sweet cherry cultivation.