In situ hybridization study of the rice phloem thioredoxin h mRNA accumulation - possible involvement in the differentiation of vascular tissues

Thioredoxin (TRX) h was identified as a major protein in rice (Oryza satira L. cv. Kantou) phloem sap. Accumulation of TRX h mRNA in fully expanded ri ce leaves was detected only in the companion cells. To clarify the role of TRY h in phloem development, we performed in situ hybridization of TRX h mR NA in rice plants during the course of vascular development. TRX h mRNA,was detected in all cell types at an early stage of development and became gra dually confined to the companion cells in later stages. The possible roles of TRS h in vascular development are discussed.