Real-time [C]methionine translocation in barley in relation to mugineic acid phytosiderophore biosynthesis

Bughio, N.*; Nakanishi, Hiromi*; Kiyomiya, Shoichiro*; Matsuhashi, Shimpei; Ishioka, Noriko; Watanabe, Satoshi; Uchida, Hiroshi*; Tsuji, Atsunori*; Osa, Akihiko  ; Kume, Tamikazu; Hashimoto, Shoji; Sekine, Toshiaki; Mori, Satoshi*

[C]Methionine ([C]Met) was supplied through barley roots and the C signal was follwoed using a real-time imaging system (PETIS), with subsequent development of autoradiographic images of the whole plant. In all cases, [C]Met was first translocated to the discrimination center, and this part was strongly labeled. Met absorbed by roots of the plants was subsequently translocated to other parts of the plant. In Fe-deficient (-Fe) barley plants, a drastic reduction in [C]Met translocation from the roots to the shoot was observed, while a greater amount of C was found in the leaves of Fe-sufficient or Met-pretreated -Fe plants. Treatment of -Fe plants with amiooxyacetic acid increased the translocation of [C]Met to the shoot. The retention of exogenously supplied [C]Met in the roots of -Fe barley indicates that the Met is used in the biosynthesis of mugineic acid (MA) in barley roots. This and the absence of Met movement from shoots to the roots suggest that the MA phytosiderophores precursor Met originates in the roots of plants.