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The F-box protein MAX2 contributes to resistance to bacterial phytopathogens in Arabidopsis thaliana.

Piisilä M, Keceli MA, Brader G, Jakobson L, Jõesaar I, Sipari N, Kollist H, Palva ET, Kariola T - BMC Plant Biol. (2015)

Bottom Line: Interestingly, max2 mutant plants showed increased susceptibility to the bacterial necrotroph Pectobacterium carotovorum as well as to the hemi-biotroph Pseudomonas syringae but not to the fungal necrotroph Botrytis cinerea. max2 mutant phenotype was associated with constitutively increased stomatal conductance and decreased tolerance to apoplastic ROS but also with alterations in hormonal balance.We conclude that the increased susceptibility to P. syringae and P. carotovorum is due to increased stomatal conductance in max2 mutants promoting pathogen entry into the plant apoplast.Additional factors contributing to pathogen susceptibility in max2 plants include decreased tolerance to pathogen-triggered apoplastic ROS and alterations in hormonal signaling.

View Article: PubMed Central - PubMed

ABSTRACT

Background: The Arabidopsis thaliana F-box protein MORE AXILLARY GROWTH2 (MAX2) has previously been characterized for its role in plant development. MAX2 appears essential for the perception of the newly characterized phytohormone strigolactone, a negative regulator of polar auxin transport in Arabidopsis.

Results: A reverse genetic screen for F-box protein mutants altered in their stress responses identified MAX2 as a component of plant defense. Here we show that MAX2 contributes to plant resistance against pathogenic bacteria. Interestingly, max2 mutant plants showed increased susceptibility to the bacterial necrotroph Pectobacterium carotovorum as well as to the hemi-biotroph Pseudomonas syringae but not to the fungal necrotroph Botrytis cinerea. max2 mutant phenotype was associated with constitutively increased stomatal conductance and decreased tolerance to apoplastic ROS but also with alterations in hormonal balance.

Conclusions: Our results suggest that MAX2 previously characterized for its role in regulation of polar auxin transport in Arabidopsis, and thus plant development also significantly influences plant disease resistance. We conclude that the increased susceptibility to P. syringae and P. carotovorum is due to increased stomatal conductance in max2 mutants promoting pathogen entry into the plant apoplast. Additional factors contributing to pathogen susceptibility in max2 plants include decreased tolerance to pathogen-triggered apoplastic ROS and alterations in hormonal signaling.

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Impaired stomatal function inmax2mutants. Four-week old wild-type Col-0 and max2 lines were assessed for their stomatal function. A) Stomatal conductance of four-week old non-treated Col-0, max2-1 and max2-4 plants were measured with a porometer. For each line 5 plants were used in each experiment and the results are shown as means ± SE. Experiments were repeated 5 times with similar results. **P < 0.01; two-tailed t test. B) Four-week old soil-grown Col-0 and max2 plants’ fresh weight change was measured by cutting the leaves and leaving them to dry for 4 h. For each line 5 plants were used in each experiment and the results are shown as means ± SE. Experiments were repeated 5 times with similar results.
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Fig3: Impaired stomatal function inmax2mutants. Four-week old wild-type Col-0 and max2 lines were assessed for their stomatal function. A) Stomatal conductance of four-week old non-treated Col-0, max2-1 and max2-4 plants were measured with a porometer. For each line 5 plants were used in each experiment and the results are shown as means ± SE. Experiments were repeated 5 times with similar results. **P < 0.01; two-tailed t test. B) Four-week old soil-grown Col-0 and max2 plants’ fresh weight change was measured by cutting the leaves and leaving them to dry for 4 h. For each line 5 plants were used in each experiment and the results are shown as means ± SE. Experiments were repeated 5 times with similar results.

Mentions: Both ozone as well as pathogens can enter the plant apoplast via natural openings such as stomata [6,42]. We hypothesized that besides increased sensitivity to apoplastic ROS, the sensitivity of max2 plants to ozone could be partly due to altered stomatal function. To validate this hypothesis we first measured stomatal conductance of max2 and wild-type plants with a porometer. Indeed, under normal growth conditions the stomata of max2 mutant plants were significantly more open in comparison to those of wild-type plants (Figure 3A).Figure 3


The F-box protein MAX2 contributes to resistance to bacterial phytopathogens in Arabidopsis thaliana.

Piisilä M, Keceli MA, Brader G, Jakobson L, Jõesaar I, Sipari N, Kollist H, Palva ET, Kariola T - BMC Plant Biol. (2015)

Impaired stomatal function inmax2mutants. Four-week old wild-type Col-0 and max2 lines were assessed for their stomatal function. A) Stomatal conductance of four-week old non-treated Col-0, max2-1 and max2-4 plants were measured with a porometer. For each line 5 plants were used in each experiment and the results are shown as means ± SE. Experiments were repeated 5 times with similar results. **P < 0.01; two-tailed t test. B) Four-week old soil-grown Col-0 and max2 plants’ fresh weight change was measured by cutting the leaves and leaving them to dry for 4 h. For each line 5 plants were used in each experiment and the results are shown as means ± SE. Experiments were repeated 5 times with similar results.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4340836&req=5

Fig3: Impaired stomatal function inmax2mutants. Four-week old wild-type Col-0 and max2 lines were assessed for their stomatal function. A) Stomatal conductance of four-week old non-treated Col-0, max2-1 and max2-4 plants were measured with a porometer. For each line 5 plants were used in each experiment and the results are shown as means ± SE. Experiments were repeated 5 times with similar results. **P < 0.01; two-tailed t test. B) Four-week old soil-grown Col-0 and max2 plants’ fresh weight change was measured by cutting the leaves and leaving them to dry for 4 h. For each line 5 plants were used in each experiment and the results are shown as means ± SE. Experiments were repeated 5 times with similar results.
Mentions: Both ozone as well as pathogens can enter the plant apoplast via natural openings such as stomata [6,42]. We hypothesized that besides increased sensitivity to apoplastic ROS, the sensitivity of max2 plants to ozone could be partly due to altered stomatal function. To validate this hypothesis we first measured stomatal conductance of max2 and wild-type plants with a porometer. Indeed, under normal growth conditions the stomata of max2 mutant plants were significantly more open in comparison to those of wild-type plants (Figure 3A).Figure 3

Bottom Line: Interestingly, max2 mutant plants showed increased susceptibility to the bacterial necrotroph Pectobacterium carotovorum as well as to the hemi-biotroph Pseudomonas syringae but not to the fungal necrotroph Botrytis cinerea. max2 mutant phenotype was associated with constitutively increased stomatal conductance and decreased tolerance to apoplastic ROS but also with alterations in hormonal balance.We conclude that the increased susceptibility to P. syringae and P. carotovorum is due to increased stomatal conductance in max2 mutants promoting pathogen entry into the plant apoplast.Additional factors contributing to pathogen susceptibility in max2 plants include decreased tolerance to pathogen-triggered apoplastic ROS and alterations in hormonal signaling.

View Article: PubMed Central - PubMed

ABSTRACT

Background: The Arabidopsis thaliana F-box protein MORE AXILLARY GROWTH2 (MAX2) has previously been characterized for its role in plant development. MAX2 appears essential for the perception of the newly characterized phytohormone strigolactone, a negative regulator of polar auxin transport in Arabidopsis.

Results: A reverse genetic screen for F-box protein mutants altered in their stress responses identified MAX2 as a component of plant defense. Here we show that MAX2 contributes to plant resistance against pathogenic bacteria. Interestingly, max2 mutant plants showed increased susceptibility to the bacterial necrotroph Pectobacterium carotovorum as well as to the hemi-biotroph Pseudomonas syringae but not to the fungal necrotroph Botrytis cinerea. max2 mutant phenotype was associated with constitutively increased stomatal conductance and decreased tolerance to apoplastic ROS but also with alterations in hormonal balance.

Conclusions: Our results suggest that MAX2 previously characterized for its role in regulation of polar auxin transport in Arabidopsis, and thus plant development also significantly influences plant disease resistance. We conclude that the increased susceptibility to P. syringae and P. carotovorum is due to increased stomatal conductance in max2 mutants promoting pathogen entry into the plant apoplast. Additional factors contributing to pathogen susceptibility in max2 plants include decreased tolerance to pathogen-triggered apoplastic ROS and alterations in hormonal signaling.

Show MeSH
Related in: MedlinePlus