Methods and compositions for increasing amino acid and protein content in plants

A method of making a modified plant with high seed protein content compared to the seed protein content of a nonmodified plant, the method comprising:

• (a) crossing a first plant comprising a deletion, insertion, or substitution of a nucleotide in (i) a genomic sequence encoding cystathionine gamma-synthase (CGS), the modification resulting in suppression of the feedback regulation of the same while retaining enzymatic activity, and/or (ii) a genomic sequence encoding a low methionine content seed storage protein, the modification resulting in suppression of the activity of the same, with a second plant;
• and (b) selecting a progeny plant, or plant part thereof, with high protein content for further breeding.

A modified CGS polynucleotide comprising an in-frame insertion or deletion in the MTO1 region so that feedback inhibition of expression is suppressed.

A modified 7S polynucleotide comprising an insertion, deletion, or substitution that suppresses activity of the polynucleotide.

A method of producing a plant cell having increased protein content, the method comprising:

• introducing a double-strand-break-inducing (DSB-inducing) agent to a plant cell, wherein the DSB-inducing agent creates a double-strand break in an endogenous CGS gene and/or a low methionine content seed storage protein gene in the genome of the plant, wherein the repair of the DSB results in the production of a modified polynucleotide, and wherein the production of the modified polynucleotide produces increased protein content in the seed.

A polynucleotide construct comprising a sequence encoding a guide RNA which targets an endogenous CGS gene and/or a low methionine content storage polypeptide gene when expressed in a plant cell and thereby generates a modified endogenous CGS gene and/or a low methionine content storage polypeptide gene.