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Molecular and Physiological Characterization of a Transposon Insertion Mutant of Δ1-Pyrroline-5-Carboxylate Synthetase Gene of Medicago truncatula

초록/요약

Δ1-Pyrroline-5-carboxylate synthetase (P5CS) enzymes, which catalyze the rate-limiting step of proline biosynthesis, are encoded by three closely related genes, MtP5CS1, MtP5CS2, and MtP5CS3, in Medicago truncatula. Transcription of MtP5CS2 and MtP5CS3 is significantly increased by drought and salinity, suggesting that these genes play important roles in the regulation of proline accumulation under environmental stress conditions. Herein a mutant of MtP5CS3 was characterized at the genetic, molecular and physiological levels. A transposon insertion mutant of MtP5CS3 (Mtp5cs3) resulted in a decrease in stress-induced proline synthesis and hypersensitivity to salt and drought stresses. Externally supplied proline and ectopically expressed wildtype gene (MtP5CS3) via Agrobacterium rhizogenes-mediated root transformation complemented the Mtp5cs3 mutant, indicating that MtP5CS3 plays a critical role in the regulation of proline accumulation in response to salinity and low water stress. Consistently, overexpression of the wildtype MtP5CS3 gene substantially increased tolerance of M. truncatula to salinity and low water stress.

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