Strigolactones positively regulate defense against root-knot nematodes in tomato

Area of Science:

• Plant Biology
• Phytohormone Research
• Plant-Pathogen Interactions

Background:

• Strigolactones (SLs) are plant hormones derived from carotenoids, influencing growth and arbuscular mycorrhizal fungi (AMF) symbiosis.
• The role of SLs in plant defense against soil-borne pathogens, particularly nematodes, remains largely unexplored.

Purpose of the Study:

• To investigate the function of strigolactones in tomato (Solanum lycopersicum) defense against root-knot nematodes (RKNs; Meloidogyne incognita).
• To elucidate the molecular mechanisms underlying SL-mediated plant defense, including interactions with jasmonic acid (JA) and abscisic acid (ABA).

Main Methods:

• Induction of SL biosynthesis in tomato roots upon RKN infection was assessed.
• Gene silencing of SL biosynthesis and application of the SL analog racGR24 were used to modulate SL levels.
• Endogenous levels of JA and ABA were quantified in response to RKN infection and SL treatments.
• Genetic analysis in JA-deficient and ABA-deficient mutants was performed.
• Expression of the MYC2 gene was analyzed in relation to SLs and RKN defense.

Main Results:

• RKN infection induced SL biosynthesis in tomato roots.
• Silencing SL biosynthesis genes compromised RKN defense, while racGR24 application enhanced it.
• SLs modulated JA and ABA accumulation; JA positively regulated RKN defense, while ABA negatively regulated it.
• racGR24-mediated nematode defense was dependent on JA but not ABA.
• Silencing SL biosynthesis genes led to MYC2 upregulation, which negatively regulated RKN defense.

Conclusions:

• Strigolactones play a crucial positive role in tomato defense against root-knot nematodes.
• MYC2 acts as a negative regulator of nematode defense, potentially through crosstalk with SLs, ABA, and JA.
• SLs mediate plant immunity by modulating key defense hormone pathways.