Both tryptophan （Trp） and auxin are essential for plant growth and Trp is a precursor for auxin biosynthesis. Concentrations of Trp and auxin need to be tightly con- trolled to ensure optimal growth and development....Both tryptophan （Trp） and auxin are essential for plant growth and Trp is a precursor for auxin biosynthesis. Concentrations of Trp and auxin need to be tightly con- trolled to ensure optimal growth and development. It has been very difficult to study the homeostasis of these two essential and inter-dependent compounds. Auxin is mainly synthesized from Trp via a two-step pathway using indole- 3-pyruvate （IPA） as the intermediate. Here we used a bacterial Trp oxidase RebO, which does not exist in Ara- bidopsis and which converts Trp to the imine form of IPA, to modulate IPA levels in Arabidopsis. Our results demonstrate that Arabidopsis plants use two strategies to ensure that no excess IPA is made from Trp. IPA is made from Trp by the TAA family of aminotransferases, which we show catalyzes the reverse reaction when IPA level is high. Moreover, excess IPA is converted back to Trp by the YAS1 aminotransferase. We show that the VASl-cat- alyzed reaction is very important for Trp homeostasis. This work not only elucidates the intricate biochemical mech- anisms that control the homeostasis of Trp, IPA, and auxin, but also provides novel tools for further biochemical studies on Tip metabolism and auxin biosynthesis in plants.展开更多
Phytohormones integrate plant growth and developmental programs with extrinsic biotic and abiotic stimuli, thereby ensuring plant architecture is optimized for the local envi- ronment. Strigolactones （SLs）, newly id...Phytohormones integrate plant growth and developmental programs with extrinsic biotic and abiotic stimuli, thereby ensuring plant architecture is optimized for the local envi- ronment. Strigolactones （SLs）, newly identified carote- noid-derived plant hormones, play non-redundant and multifaceted roles throughout the plant life cycle （de Saint Germain et al.2013）, similarly to other plant hormones.展开更多
基金supported by the NIH(R01GM114660 to YZ)supported by NIH(GM52413to JC)HHMI
文摘Both tryptophan （Trp） and auxin are essential for plant growth and Trp is a precursor for auxin biosynthesis. Concentrations of Trp and auxin need to be tightly con- trolled to ensure optimal growth and development. It has been very difficult to study the homeostasis of these two essential and inter-dependent compounds. Auxin is mainly synthesized from Trp via a two-step pathway using indole- 3-pyruvate （IPA） as the intermediate. Here we used a bacterial Trp oxidase RebO, which does not exist in Ara- bidopsis and which converts Trp to the imine form of IPA, to modulate IPA levels in Arabidopsis. Our results demonstrate that Arabidopsis plants use two strategies to ensure that no excess IPA is made from Trp. IPA is made from Trp by the TAA family of aminotransferases, which we show catalyzes the reverse reaction when IPA level is high. Moreover, excess IPA is converted back to Trp by the YAS1 aminotransferase. We show that the VASl-cat- alyzed reaction is very important for Trp homeostasis. This work not only elucidates the intricate biochemical mech- anisms that control the homeostasis of Trp, IPA, and auxin, but also provides novel tools for further biochemical studies on Tip metabolism and auxin biosynthesis in plants.
文摘Phytohormones integrate plant growth and developmental programs with extrinsic biotic and abiotic stimuli, thereby ensuring plant architecture is optimized for the local envi- ronment. Strigolactones （SLs）, newly identified carote- noid-derived plant hormones, play non-redundant and multifaceted roles throughout the plant life cycle （de Saint Germain et al.2013）, similarly to other plant hormones.
