Paper · 2026 · PLANT PHYSIOLOGY

The regulatory module MsSPX4/MsPHL11–MsWRKY91 mediates low-phosphorus-induced anthocyanin synthesis in Malus spectabilis leaves

Jun Wei; Zenan Wang; Yuan Li; et al.

7
claims
11
verbatim quotes
1
citations
2
research areas
—
Not open access

Abstract

Phosphorus (P) is a macronutrient necessary for plant growth and development. Phosphorus deficiency usually causes changes in plant secondary metabolites, mainly including anthocyanin synthesis. However, the regulatory mechanism of anthocyanin synthesis in Malus spectabilis leaves under low-phosphorus conditions remains unclear. In this study, anthocyanin accumulation in M. spectabilis leaves gradually increased as phosphorus application decreased, reaching a maximum anthocyanin concentration at 300 µM phosphorus. Through transcriptome sequencing, MsSPX4 was identified as a key regulatory factor for anthocyanin synthesis under low-phosphorus conditions. The protein complex MsSPX4-MsPHL11 was confirmed through Y2H, BiFC, and LCI assays, and its function was validated through transient and stable transformation experiments in Malus spp. Under conditions of sufficient Pi, MsSPX4 inhibited MsPHL11 activity by interacting with MsPHL11, whereas phosphorus starvation disrupted the MsSPX4/MsPHL11 complex, alleviating the inhibitory effect on MsPHL11. MsPHL11 bound to the P1BS element on the MsWRKY91 promoter to activate MsWRKY91 expression. Furthermore, MsWRKY91 activated MsF3'H expression by binding to the W-box element on the MsF3'H promoter, thereby positively regulating anthocyanin biosynthesis. Overexpression of MsPHL11 promoted the expression of genes related to phosphorus metabolism and transport, thereby increasing M. 'Gala' low-phosphorus resistance. By contrast, MsSPX4-stabilized transgenic M. 'Gala' lines exhibited lower phosphorus resistance. Our results elucidate the mechanism by which the MsSPX4/MsPHL11-MsWRKY91 module regulates anthocyanin synthesis in M. spectabilis leaves under low-phosphorus conditions. These findings provide a reference for further exploration of the molecular mechanism of anthocyanin synthesis in plants under low-phosphorus conditions.

Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher. Read at the source ↗

The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.

Claims 7

Associationobservedoriginal resultmeasured

Claim · model-written summary

Anthocyanin accumulation in M. spectabilis leaves increased as phosphorus application decreased.

Taxon
M. spectabilisMalus spectabilise1
Treatment
phosphorus application decreasede1
Outcome
anthocyanin accumulatione1
Direction
increasede1
Value
300 µM phosphoruse1

Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Malus spectabilis
Malus spectabilis · TaxonJeffrey O. Gustafson · CC BY-SA 3.0 · Wikimedia Commons ↗

Verbatim

e1

“anthocyanin accumulation in M. spectabilis leaves gradually increased as phosphorus application decreased, reaching a maximum anthocyanin concentration at 300 µM phosphorus”

✓ located verbatim in the source · abstract, characters 346–518 · show in text ↑
Mechanismobservedoriginal resultmeasured

Claim · model-written summary

MsSPX4 was identified as a key regulatory factor for anthocyanin synthesis under low-phosphorus conditions.

Taxon
Malus sppMaluse4
Gene
MsSPX4e2
Outcome
anthocyanin synthesise2

Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Malus
Malus · Taxon · picture of the genus (one of its species)Bruce Marlin · CC BY 3.0 · Wikimedia Commons ↗

Verbatim

e2

“MsSPX4 was identified as a key regulatory factor for anthocyanin synthesis under low-phosphorus conditions”

✓ located verbatim in the source · abstract, characters 554–660 · show in text ↑
e4

“transient and stable transformation experiments in Malus spp”

✓ located verbatim in the source · abstract, characters 785–845 · show in text ↑
Mechanismauthor interpretationoriginal resultmeasured

Claim · model-written summary

Under sufficient Pi, MsSPX4 inhibited MsPHL11 activity, while phosphorus starvation disrupted the MsSPX4/MsPHL11 complex.

Taxon
Malus sppMaluse4
Gene
MsSPX4e3
Compound
Pie3
Outcome
MsPHL11 activitye3

Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Malus
Malus · Taxon · picture of the genus (one of its species)Bruce Marlin · CC BY 3.0 · Wikimedia Commons ↗

Verbatim

e3

“Under conditions of sufficient Pi, MsSPX4 inhibited MsPHL11 activity by interacting with MsPHL11, whereas phosphorus starvation disrupted the MsSPX4/MsPHL11 complex”

✓ located verbatim in the source · abstract, characters 847–1011 · show in text ↑
e4

“transient and stable transformation experiments in Malus spp”

✓ located verbatim in the source · abstract, characters 785–845 · show in text ↑
Mechanismobservedoriginal resultmeasured

Claim · model-written summary

MsPHL11 binds the P1BS element on the MsWRKY91 promoter to activate MsWRKY91 expression.

Taxon
Malus sppMaluse4
Interactor
MsWRKY91e5
Gene
MsPHL11e5
Outcome
MsWRKY91 expressione5

Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Malus
Malus · Taxon · picture of the genus (one of its species)Bruce Marlin · CC BY 3.0 · Wikimedia Commons ↗

Verbatim

e5

“MsPHL11 bound to the P1BS element on the MsWRKY91 promoter to activate MsWRKY91 expression”

✓ located verbatim in the source · abstract, characters 1059–1149 · show in text ↑
e4

“transient and stable transformation experiments in Malus spp”

✓ located verbatim in the source · abstract, characters 785–845 · show in text ↑
Mechanismobservedoriginal resultpositivemeasured

Claim · model-written summary

MsWRKY91 activates MsF3'H expression through the W-box element and positively regulates anthocyanin biosynthesis.

Taxon
Malus sppMaluse4
Gene
MsF3'He6
Outcome
anthocyanin biosynthesise6
Direction
positively regulatinge6

Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Malus
Malus · Taxon · picture of the genus (one of its species)Bruce Marlin · CC BY 3.0 · Wikimedia Commons ↗

Verbatim

e6

“MsWRKY91 activated MsF3'H expression by binding to the W-box element on the MsF3'H promoter, thereby positively regulating anthocyanin biosynthesis”

✓ located verbatim in the source · abstract, characters 1164–1311 · show in text ↑
e4

“transient and stable transformation experiments in Malus spp”

✓ located verbatim in the source · abstract, characters 785–845 · show in text ↑
Associationobservedoriginal resultpositivemeasured

Claim · model-written summary

Overexpression of MsPHL11 increased M. Gala low-phosphorus resistance.

Taxon
M. 'Gala'e7
Treatment
Overexpression of MsPHL11e7
Gene
MsPHL11e7
Outcome
low-phosphorus resistancee7
Direction
increasinge7

Verbatim

e7

“Overexpression of MsPHL11 promoted the expression of genes related to phosphorus metabolism and transport, thereby increasing M. 'Gala' low-phosphorus resistance”

✓ located verbatim in the source · abstract, characters 1313–1474 · show in text ↑
Associationobservedoriginal resultnegativemeasured

Claim · model-written summary

MsSPX4-stabilized transgenic M. Gala lines exhibited lower phosphorus resistance.

Taxon
M. 'Gala'e0
Treatment
MsSPX4-stabilized transgenice0
Gene
MsSPX4e0
Outcome
phosphorus resistancee0
Direction
lowere0

Verbatim

e0

“MsSPX4-stabilized transgenic M. 'Gala' lines exhibited lower phosphorus resistance”

✓ located verbatim in the source · abstract, characters 1489–1571 · show in text ↑