Targeting of flavodoxin to chloroplasts of mesophyll but not bundle sheath maize cells confers increased drought tolerance

DEMARCHI, MARIANA; ROCIO ARCE; MABEL CAMPI; JUAN PIERELLA KARLUSICH; MOHAMMAD-REZA HAJIREZAEI; MICHAEL MELZER; ANABELLA LODEYRO; RAQUEL CHAN; NÉSTOR CARRILLO

New Phytologist

John Wiley and Sons Inc

Año: 2023 vol. 240 p. 2179 - 2184

The cyanobacterial electron shuttle flavodoxin confers increased tolerance to multiple environmental stresses when introduced in chloroplasts from C3 plants, by relieving excess of excitation energy from the photosynthetic electron transport chain (PETC). Flavodoxin effects on stress tolerance of C4 plants displaying different photosynthetic pathways in mesophyll (Ms) and bundle sheath (BS) cells (mostly lineal and cyclic, respectively), remain unknown. The use of tissue-specific transformation in maize has been sparse, especially for photosynthetic studies. We expressed plastid-targeted flavodoxin differentially in maize Ms and BS cells by using tissue-specific promoters and transit peptides. We show that Ms lines exhibited increased tolerance to drought and oxidative stress, whereas BS plants displayed wild-type levels of damage, suggesting that flavodoxin interaction with the lineal PETC of Ms chloroplasts was critical for its protective effect, while interaction with the cyclic pathway of BS plastids was inconsequential. Our report identifies the type of intervention required to improve stress tolerance in maize plants using the flavodoxin approach, thus providing a more effective rationale to engineer this most important crop for better growth and yield in sub-optimal environments. Moreover, combination of tissue-specific expression with alternative electron shuttles such as flavodoxin provides a research tool to investigate the complex relationship between environmental hardships and C4 photosynthesis.