Constitutively wilted 1, a member of the rice YUCCA gene family, is required for maintaining water homeostasis and an appropriate root to shoot ratio.
Increasing its root to shoot ratio is a plant strategy for restoring water homeostasis in response to the long-term imposition of mild water stress. In addition to its important role in diverse fundamental processes, indole-3-acetic acid (IAA) is involved in root growth and development. Recent extensive characterizations of the YUCCA gene family in Arabidopsis and rice have elucidated that member's function in a tryptophan-dependent IAA biosynthetic pathway. Through forward- and reverse-genetics screening, we have isolated Tos17 and T-DNA insertional rice mutants in a CONSTITUTIVELY WILTED1 (COW1) gene, which encodes a new member of the YUCCA protein family. Homozygous plants with either a Tos17 or T-DNA-inserted allele of OsCOW1 exhibit phenotypes of rolled leaves, reduced leaf widths, and lower root to shoot ratios. These phenotypes are evident in seedlings as early as 7-10 d after germination, and remain until maturity. When oscow1 seedlings are grown under low-intensity light and high relative humidity, the rolled-leaf phenotype is greatly alleviated. For comparison, in such conditions, the transpiration rate for WT leaves decreases approx. 5- to 10-fold, implying that this mutant trait results from wilting rather than being a morphogenic defect. Furthermore, a lower turgor potential and transpiration rate in their mature leaves indicates that oscow1 plants are water-deficient, due to insufficient water uptake that possibly stems from that diminished root to shoot ratio. Thus, our observations suggest that OsCOW1-mediated IAA biosynthesis plays an important role in maintaining root to shoot ratios and, in turn, affects water homeostasis in rice.
Woo
Young-Min
YM
National Research Laboratory of Plant Functional Genomics, Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Korea.
Park
Hee-Jin
HJ
Su'udi
Mukhamad
M
Yang
Jung-Il
JI
Park
Jong-Jin
JJ
Back
Kyoungwhan
K
Park
Yong-Mok
YM
An
Gynheung
G
D000595:Amino Acid Sequence; D004269:DNA, Bacterial / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D006706:Homeostasis; D007210:Indoleacetic Acids / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D012275:Oryza / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D010105:Oxygenases / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010802:Phylogeny; D018517:Plant Roots / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D018520:Plant Shoots / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014363:Tryptamines / Q000096:biosynthesis; D014867:Water / Q000378:metabolism*
D004269:DNA, Bacterial; D007210:Indoleacetic Acids; C036483:T-DNA; D014363:Tryptamines; D014867:Water; C030820:tryptamine; C030737:indoleacetic acid; D010105:Oxygenases