TY - JOUR

T1 - New insights into the genetic manipulation of the R2R3-MYB and CHI gene families on anthocyanin pigmentation in Petunia hybrida

AU - Li, Guo

AU - Michaelis, Dietz Felix

AU - Huang, Junjie

AU - Serek, Margrethe

AU - Gehl, Christian

N1 - Funding Information: The authors would like to thank our student Juliane Warnecke, the laboratory staff, and the gardeners of the Section Floriculture at the Leibniz University Hannover for technical assistance. Guo Li gratefully acknowledge financial support from China Scholarship Council (CSC) .

PY - 2023/10

Y1 - 2023/10

N2 - Several R2R3-MYB genes control anthocyanin pigmentation in petunia, and ANTHOCYANIN-2 (AN2) is treated as the main player in petal limbs. However, the actual roles of R2R3-MYBs in the coloration of different floral tissues in the so called “darkly-veined” petunias are still not clear. The genetic background and expression of AN2 paralogs from various petunias with different color patterns were identified. All “darkly-veined” genotypes have the identical mutation in the AN2 gene, but express a different functional paralog – ANTHOCYANIN-4 (AN4) – abundantly in flowers. Constitutive overexpression of PhAN4 in this petunia resulted not only in a fully colored flower but also in a clearly visible pigmentation in the green tissue and roots, which can be rapidly increased by stress conditions. Suppression of AN4 gene resulted in discolored petals and whitish anthers. Interestingly, when a similar white flower phenotype was achieved by knockout of an essential structural gene of anthocyanin biosynthesis – CHALCONE ISOMERASE-A (CHI-A) – the plant responded directly by upregulating of another paralogs – DEEP PURPLE (DPL) and PURPLE HAZE (PHZ). Moreover, we also found that CHI–B can partially substitute for CHI-A in anthers, but not in vegetative tissues. Further, no significant effects on the longevity of white or enhanced colored flowers were observed compared with the wild type. We concluded that endogenous up-regulation of AN4 leads to the restoration of petal color in the “darkly-veined” phenotypes as a result of the breeding process under human selection, and CHI–B is a backup for CHI-A acitvity in some floral tissues.

AB - Several R2R3-MYB genes control anthocyanin pigmentation in petunia, and ANTHOCYANIN-2 (AN2) is treated as the main player in petal limbs. However, the actual roles of R2R3-MYBs in the coloration of different floral tissues in the so called “darkly-veined” petunias are still not clear. The genetic background and expression of AN2 paralogs from various petunias with different color patterns were identified. All “darkly-veined” genotypes have the identical mutation in the AN2 gene, but express a different functional paralog – ANTHOCYANIN-4 (AN4) – abundantly in flowers. Constitutive overexpression of PhAN4 in this petunia resulted not only in a fully colored flower but also in a clearly visible pigmentation in the green tissue and roots, which can be rapidly increased by stress conditions. Suppression of AN4 gene resulted in discolored petals and whitish anthers. Interestingly, when a similar white flower phenotype was achieved by knockout of an essential structural gene of anthocyanin biosynthesis – CHALCONE ISOMERASE-A (CHI-A) – the plant responded directly by upregulating of another paralogs – DEEP PURPLE (DPL) and PURPLE HAZE (PHZ). Moreover, we also found that CHI–B can partially substitute for CHI-A in anthers, but not in vegetative tissues. Further, no significant effects on the longevity of white or enhanced colored flowers were observed compared with the wild type. We concluded that endogenous up-regulation of AN4 leads to the restoration of petal color in the “darkly-veined” phenotypes as a result of the breeding process under human selection, and CHI–B is a backup for CHI-A acitvity in some floral tissues.

KW - ANTHOCYANIN-4 (AN4)

KW - CHALCONE ISOMERASE (CHI)

KW - CRISPR/Cas9

KW - Flower coloration

KW - R2R3-MYB transcription factor

KW - Sucrose induction

UR - http://www.scopus.com/inward/record.url?scp=85169934134&partnerID=8YFLogxK

U2 - 10.1016/j.plaphy.2023.108000

DO - 10.1016/j.plaphy.2023.108000

M3 - Article

AN - SCOPUS:85169934134

VL - 203

JO - Plant physiology and biochemistry

JF - Plant physiology and biochemistry

SN - 0981-9428

M1 - 108000

ER -