Identification of a sequence motif of the rice Pho1 L80 that potentially modulates grain starch metabolism and floral timing
- 1Washington State University
Abstract
Plastidial phosphorylase (Pho1) regulates starch metabolism and also modulates photosystem I (PSI) activity. In rice, Pho1 contains an 80 amino acid intrinsically disordered region (IDR), L80, that acts as a negative regulator. While total removal of the IDR boosts seedling growth, flowering time, overall biomass, and grain yield and alters PSI redox properties, the precise underlying regulatory basis remains unclear. To pinpoint IDR regulatory elements, four Pho1 partial-IDR deletion variants ({Delta}N, {Delta}C, {Delta}M, and {Delta}N and {Delta}C) were evaluated. Lines carrying {Delta}M and {Delta}C exhibited enhanced starch metabolism, yielding larger, heavier grains, and flowered 5 to10 days earlier than wild type. Both d{delta}M and {Delta}C share an acidic motif, (E/V)SEEV, identifying it as a primary negative regulator of starch synthesis and floral timing. By contrast, no partial deletion fully mirrored the PSI redox modifications of Pho1{Delta}L80. These results demonstrate that starch biosynthesis and flowering are governed by one or more discrete sequence motifs within the middle and C-terminal regions, whereas PSI modulation likely requires the structural integrity of the intact IDR.
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BibTeX
@misc{ng2026identification,
title = {{Identification of a sequence motif of the rice Pho1 L80 that potentially modulates grain starch metabolism and floral timing}},
author = {C.-y. Ng and S.-k. Hwang and M. Wood and H. Kirchhoff and T. W. Okita},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.19.751552},
url = {https://www.biorxiv.org/content/10.64898/2026.09.19.751552v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Identification of a sequence motif of the rice Pho1 L80 that potentially modulates grain starch metabolism and floral timing
AU - C.-y. Ng
AU - S.-k. Hwang
AU - M. Wood
AU - H. Kirchhoff
AU - T. W. Okita
PY - 2026
DA - 2026/09/19
PB - bioRxiv
DO - 10.64898/2026.09.19.751552
UR - https://www.biorxiv.org/content/10.64898/2026.09.19.751552v1
AB - Plastidial phosphorylase (Pho1) regulates starch metabolism and also modulates photosystem I (PSI) activity. In rice, Pho1 contains an 80 amino acid intrinsically disordered region (IDR), L80, that acts as a negative regulator. While total removal of the IDR boosts seedling growth, flowering time, overall biomass, and grain yield and alters PSI redox properties, the precise underlying regulatory basis remains unclear. To pinpoint IDR regulatory elements, four Pho1 partial-IDR deletion variants ({Delta}N, {Delta}C, {Delta}M, and {Delta}N and {Delta}C) were evaluated. Lines carrying {Delta}M and {Delta}C exhibited enhanced starch metabolism, yielding larger, heavier grains, and flowered 5 to10 days earlier than wild type. Both d{delta}M and {Delta}C share an acidic motif, (E/V)SEEV, identifying it as a primary negative regulator of starch synthesis and floral timing. By contrast, no partial deletion fully mirrored the PSI redox modifications of Pho1{Delta}L80. These results demonstrate that starch biosynthesis and flowering are governed by one or more discrete sequence motifs within the middle and C-terminal regions, whereas PSI modulation likely requires the structural integrity of the intact IDR.
ER -