l ‐Tyrosine is an essential aromatic amino acid required for the synthesis of proteins and a diverse array of plant natural products; however, little is known on how the levels of tyrosine are controlled
in planta and linked to overall growth and development. Most plants synthesize tyrosine by TyrA arogenate dehydrogenases, which are strongly feedback‐inhibited by tyrosine and encoded by
TyrA1 and
TyrA2 genes in
Arabidopsis thaliana. While TyrA enzymes have been extensively characterized at biochemical levels, their
in planta functions remain uncertain. Here we found that
TyrA1 suppression reduces seed yield due to impaired anther dehiscence, whereas
TyrA2 knockout leads to slow growth with reticulate leaves. The
tyra2 mutant phenotypes were exacerbated by
TyrA1 suppression and rescued by the expression of
TyrA2,
TyrA1 or tyrosine feeding. Low‐light conditions synchronized the
tyra2 and wild‐type growth, and ameliorated the
tyra2 leaf reticulation. After shifting to normal light,
tyra2 transiently decreased tyrosine and subsequently increased aspartate before the appearance of the leaf phenotypes. Overexpression of the deregulated TyrA enzymes led to hyper‐accumulation of tyrosine, which was also accompanied by elevated aspartate and reticulate leaves. These results revealed that TyrA1 and TyrA2 have distinct and overlapping functions in flower and leaf development, respectively, and that imbalance of tyrosine, caused by altered TyrA activity and regulation, impacts growth and development of Arabidopsis. The findings provide critical bases for improving the production of tyrosine and its derived natural products, and further elucidating the coordinated metabolic and physiological processes to maintain tyrosine levels in plants.
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