Protein Targeting to Starch 1 is essential for starchy endosperm development in barley

TY - JOUR

T1 - Protein Targeting to Starch 1 is essential for starchy endosperm development in barley

AU - Zhong, Yingxin

AU - Blennow, Andreas

AU - Kofoed-Enevoldsen, Olivia

AU - Jiang, Dong

AU - Hebelstrup, Kim Henrik

PY - 2019/1/15

Y1 - 2019/1/15

N2 - Plant starch is the main energy contributor to the human diet. Its biosynthesis is catalyzed and regulated by co-ordinated actions of several enzymes. Recently, a factor termed Protein Targeting to Starch 1 (PTST1) was identified as being required for correct granule-bound starch synthase (GBSS) localization and demonstrated to be crucial for amylose synthesis in Arabidopsis. However, the function of its homologous protein in storage tissues (e.g. endosperm) is unknown. We identified a PTST1 homolog in barley and it was found to contain a crucial coiled-coil domain and carbohydrate-binding module. We demonstrated the interaction between PTST1 and GBSS1 by fluorescence resonance energy transfer (FRET) in barley endosperm. By tagging PTST1 with the fluorophore mCherry, we observed that it is localized in the stroma of barley endosperm amyloplasts. PTST1 overexpression in endosperm increased endogenous gbss1a gene expression and amylose content. Gbss1a and ptst1 mutants were generated using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-related protein 9 (Cas9)-based targeted mutagenesis. Homozygous gbss1a mutants showed a waxy phenotype. Grains of ptst1 mutants did not accumulate any starch. These grains dried out during the desiccation stage and were unable to germinate, suggesting that PTST1 is essential for development of starchy endosperm and viable grains.

AB - Plant starch is the main energy contributor to the human diet. Its biosynthesis is catalyzed and regulated by co-ordinated actions of several enzymes. Recently, a factor termed Protein Targeting to Starch 1 (PTST1) was identified as being required for correct granule-bound starch synthase (GBSS) localization and demonstrated to be crucial for amylose synthesis in Arabidopsis. However, the function of its homologous protein in storage tissues (e.g. endosperm) is unknown. We identified a PTST1 homolog in barley and it was found to contain a crucial coiled-coil domain and carbohydrate-binding module. We demonstrated the interaction between PTST1 and GBSS1 by fluorescence resonance energy transfer (FRET) in barley endosperm. By tagging PTST1 with the fluorophore mCherry, we observed that it is localized in the stroma of barley endosperm amyloplasts. PTST1 overexpression in endosperm increased endogenous gbss1a gene expression and amylose content. Gbss1a and ptst1 mutants were generated using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-related protein 9 (Cas9)-based targeted mutagenesis. Homozygous gbss1a mutants showed a waxy phenotype. Grains of ptst1 mutants did not accumulate any starch. These grains dried out during the desiccation stage and were unable to germinate, suggesting that PTST1 is essential for development of starchy endosperm and viable grains.

UR - http://www.scopus.com/inward/record.url?scp=85059495842&partnerID=8YFLogxK

U2 - 10.1093/jxb/ery398

DO - 10.1093/jxb/ery398

M3 - Journal article

C2 - 30407538

AN - SCOPUS:85059495842

SN - 0022-0957

VL - 70

SP - 485

EP - 496

JO - Journal of Experimental Botany

JF - Journal of Experimental Botany

IS - 2

ER -