Abstract
BACKGROUND: Tocopherols are a class of lipid-soluble compounds that have multiple functional roles in plants and exhibit vitamin E activity, an essential nutrient for human and animal health. The tocopherol biosynthetic pathway is conserved across the plant kingdom, but source of the key tocopherol pathway precursor, phytol, is unclear. Two protochlorophyllide reductases (POR1 and POR2) were previously identified as loci controlling the natural variation of total tocopherols in maize grain, a non-photosynthetic tissue. POR1 and POR2 are key genes in chlorophyll biosynthesis yet the contribution of the chlorophyll biosynthetic pathway to tocopherol biosynthesis is still not understood. RESULTS: We took two approaches to alter the activity of these two POR genes within kernel tissue, physiological treatments and CRISPR/Cas9-mediated knockouts, to determine the role of chlorophyll biosynthesis for tocopherol content. Since light is required for POR enzymatic activity, we imposed a dark treatment on developing kernels, which reduced chlorophyll a and tocopherols levels in embryo tissue by 92-99% and 87-90%, respectively, compared to the light treatment. In CRISPR/Cas9-mediated knockouts, the levels of chlorophyll a and tocopherols in embryos of the por1 por2 double homozygous mutant were reduced by 98-100% and 76-83%, respectively, compared to WT. CONCLUSION: These findings demonstrate that tocopherol synthesis in maize grain depends almost entirely on phytol derived from chlorophyll biosynthesis within the embryo. POR1 and POR2 activity play crucial roles in chlorophyll biosynthesis, underscoring the importance of POR alleles and their activity in the biofortification of vitamin E levels in non-photosynthetic grain of maize.
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Claims 6
Claim · model-written summary
Dark treatment reduced embryo chlorophyll a by 92-99% versus light.
- Organ / stage
- embryo tissuee0
- Treatment
- dark treatmente0
- Outcome
- chlorophyll ae0
- Direction
- reducede0
- Value
- 92-99%e0
- Comparator
- light treatmente0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dark treatment on developing kernels, which reduced chlorophyll a and tocopherols levels in embryo tissue by 92-99% and 87-90%, respectively, compared to the light treatment.”
t0“maize grain”
Claim · model-written summary
Dark treatment reduced embryo tocopherols by 87-90% versus light.
- Organ / stage
- embryo tissuee0
- Treatment
- dark treatmente0
- Outcome
- tocopherolse0
- Direction
- reducede0
- Value
- 87-90%e0
- Comparator
- light treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dark treatment on developing kernels, which reduced chlorophyll a and tocopherols levels in embryo tissue by 92-99% and 87-90%, respectively, compared to the light treatment.”
t0“maize grain”
Claim · model-written summary
The por1 por2 double mutant had 98-100% less embryo chlorophyll a than WT.
- Material
- por1 por2 double homozygous mutante0
- Organ / stage
- embryose0
- Treatment
- por1 por2 double homozygous mutante0
- Outcome
- chlorophyll ae0
- Direction
- reducede0
- Value
- 98-100%e0
- Comparator
- WTe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chlorophyll a and tocopherols in embryos of the por1 por2 double homozygous mutant were reduced by 98-100% and 76-83%, respectively, compared to WT.”
t0“maize grain”
Claim · model-written summary
The por1 por2 double mutant had 76-83% less embryo tocopherols than WT.
- Material
- por1 por2 double homozygous mutante0
- Organ / stage
- embryose0
- Treatment
- por1 por2 double homozygous mutante0
- Outcome
- tocopherolse0
- Direction
- reducede0
- Value
- 76-83%e0
- Comparator
- WTe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chlorophyll a and tocopherols in embryos of the por1 por2 double homozygous mutant were reduced by 98-100% and 76-83%, respectively, compared to WT.”
t0“maize grain”
Claim · model-written summary
The authors conclude maize grain tocopherol synthesis depends almost entirely on embryo chlorophyll-derived phytol.
- Compound
- phytole0
- Outcome
- tocopherol synthesise0
- Qualifier
- almost entirely on phytol derived from chlorophyll biosynthesis within the embryoe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“tocopherol synthesis in maize grain depends almost entirely on phytol derived from chlorophyll biosynthesis within the embryo.”
Claim · model-written summary
POR1 and POR2 activity are crucial for chlorophyll biosynthesis.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“POR1 and POR2 activity play crucial roles in chlorophyll biosynthesis”
t0“maize grain”
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