Evolution and Functional Adaptation of Phytoplasma Effectors: A Potential Mobile Unit-Driven Perspective.

Area of Science:

• Plant pathology
• Microbial genetics
• Evolutionary biology

Background:

• Phytoplasmas exhibit significant phenotypic plasticity due to their effector proteins.
• These effectors rapidly evolve and functionally diverge, impacting host plants and vectors.

Purpose of the Study:

• To catalogue phytoplasma effectors and their targets.
• To understand the role of genome reduction and mobile genetic elements in effector evolution.
• To elucidate the evolutionary pressures shaping effector diversity and function.

Main Methods:

• Cataloguing of over 50 characterized phytoplasma effectors.
• Analysis of effector interactions with plant regulatory hubs (SPL/GATA, TCP, MADS-box, ARF).
• Population-level comparisons to assess effector distribution on mobile genetic elements (PMUs).
• Investigation of selection pressures (purifying and diversifying) on effector genes.

Main Results:

• Effectors interfere with key plant pathways, affecting morphogenesis and hormone balance.
• Phytoplasma genomes show drastic reduction balanced by PMU-mediated replication and recombination.
• Most effectors reside on PMUs, facilitating their evolution via recombination and horizontal transfer.
• Purifying selection maintains essential virulence, while diversifying selection refines host specificity and immune evasion.

Conclusions:

• Phytoplasma effector arsenal evolution is intrinsically linked to PMU dynamics.
• Understanding PMU-effector interactions offers insights into phytoplasma's molecular host manipulation strategies.
• This plasticity is crucial for phytoplasma adaptation and pathogenicity.