Ultrastructural Changes in Sunflower Chloroplasts Following Inoculation With Pseudomonas Syringae Pv. Tagetis

Abstract

Severe chlorosis and ultrastructural modifications of chloroplasts occur in sunflower in response to infection by Pseudomonas syringae pv. tagetis. Chlorosis became apparent within 2 days after the cotyledons of lO-day-old sunflower seedlings were inoculated with the bacteria. The first symptoms generally appeared in the center of leaves at the second node above the cotyledons. Leaves above the second node lost essentially all oftheir pigmentation but remained turgid and continued to expand. Grana thylakoids became dilated and separated from the granal stacks. These thylakoid membranes did not chemically breakdown as in the case in chromoplast formation or normal chloroplast senescence. Both grana and stroma thylakoid membranes coalesced to form a large membrane sheet within the plastid. The ultrastructural changes are unlike those reported to be caused by other chlorosis-inducing bacteria or chlorosis associated with normal senescence.

Growth-promoting bacteria alleviates drought stress of G. uralensis through improving photosynthesis characteristics and water status

“…B. pumilus inoculation treatment improved the integrity of chloroplast and mitochondrion structure. These observations were similar to those observed by Freeman et al (1985), who found that endophytic bacterial inoculation can improve thylakoid formation in the chloroplasts in drought-stressed sunflower plants. Moreover, chloroplasts showed reduced length and abnormal shape, which may be a sign of enhanced water loss in leaves.…”

A J Domain Virulence Effector of Pseudomonas syringae Remodels Host Chloroplasts and Suppresses Defenses

“…In any event, the targeting of chloroplast functions may be a common virulence mechanism for P. syringae. For example, some strains produce tagetotoxin that dramatically alters chloroplast morphology, resulting in large vacuole-like structures within the chloroplasts [23]. Another P. syringae phytotoxin, the polyketide coronatine, localizes to chloroplasts [24] and affects stomatal closure, providing a route for bacteria to gain access to underlying mesophyll cells [25].…”