Abstract
Leaf yellowing is among the common and easily identifiable symptoms that manifest during the invasion of phytoplasmas ( Candidatus Phytoplasma), leading to the repression of photosynthetic efficiency and losses in crop yield. Phytoplasma-secreted effectors attack several transcription factors to induce witches’ broom, phyllody and small leaves in jujube ( Ziziphus jujuba ). However, phytoplasma effector-induced leaf yellowing is not well understood. Here, the jujube witches’ broom (JWB) phytoplasma effector SJP26, which serves as a virulence factor to induce leaf yellowing in Arabidopsis thaliana and Nicotiana benthamiana , was characterized. The cytoplasmic- and nucleus-localized SJP26 encoded 136 amino acids (aa), containing one N-terminal signal peptide (1–33 aa), three α-helices and five β-sheets. SJP26 is highly expressed in JWB phytoplasma-infected leaves but is expressed at lower levels in the phloem and axillary bud. Heterologous expression of SJP26 without the signal peptide in A. thaliana resulted in a stronger ability to induce leaf yellowing than its homologues, including the SAP05 AYWB effector from the aster yellows phytoplasma strain witches’ broom, the SAP05 PnWBa effector from peanut witches’ broom phytoplasmas and the SAP05 WBDLa effector from witches’ broom disease of lime phytoplasmas. Transcriptomic analysis and pigment content measurements revealed that genes related to the chlorophyll biosynthetic pathway and chlorophyll content were significantly downregulated in the yellowed leaves of SJP26 transgenic N. benthamiana . Transformation of SJP26 in sour jujube calli confirmed the repression of gene expression related to chlorophyll biosynthesis and chlorophyll content, which were consistent with those in JWB phytoplasma-infected yellowed leaves. These findings provide insight into the mechanism underlying the effect of SJP26 on leaf yellowing in JWB phytoplasma-infected perennial woody fruit trees.
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Claims 7
Claim · model-written summary
SJP26 was localized in the cytoplasm and nucleus and encoded 136 amino acids with a signal peptide, three alpha helices and five beta sheets.
Verbatim
e0“The cytoplasmic- and nucleus-localized SJP26 encoded 136 amino acids (aa), containing one N-terminal signal peptide (1–33 aa), three α-helices and five β-sheets.”
t0“Jujube”
Claim · model-written summary
SJP26 expression was high in infected leaves and lower in phloem and axillary bud.
Verbatim
e0“SJP26 is highly expressed in JWB phytoplasma-infected leaves but is expressed at lower levels in the phloem and axillary bud”
t0“Jujube”
Claim · model-written summary
SJP26 without its signal peptide induced stronger leaf yellowing in Arabidopsis than the compared homologues.
- Taxon
- A. thaliana
Arabidopsis thalianae0 - Treatment
- Heterologous expression of SJP26 without the signal peptidee0
- Gene
- SJP26e0
- Outcome
- leaf yellowinge0
- Direction
- strongere0
- Comparator
- its homologuese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Heterologous expression of SJP26 without the signal peptide in A. thaliana resulted in a stronger ability to induce leaf yellowing than its homologues, including the SAP05 AYWB effector from the aster yellows phytoplasma strain witches’ broom, the SAP05 PnWBa effector from peanut witches’ broom phytoplasmas and the SAP05 WBDLa effector from witches’ broom disease of lime phytoplasmas”
Claim · model-written summary
Chlorophyll biosynthesis genes were significantly downregulated in yellowed SJP26 transgenic Nicotiana leaves.
- Taxon
- N. benthamiana
Nicotiana benthamianae0 - Organ / stage
- yellowed leavese0
- Gene
- genes related to the chlorophyll biosynthetic pathwaye0
- Outcome
- genes related to the chlorophyll biosynthetic pathwaye0
- Direction
- downregulatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“genes related to the chlorophyll biosynthetic pathway and chlorophyll content were significantly downregulated in the yellowed leaves of SJP26 transgenic N. benthamiana”
Claim · model-written summary
Chlorophyll content was significantly downregulated in yellowed SJP26 transgenic Nicotiana leaves.
- Taxon
- N. benthamianaNicotiana benthamianae0
- Organ / stage
- yellowed leavese0
- Outcome
- chlorophyll contente0
- Direction
- downregulatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“genes related to the chlorophyll biosynthetic pathway and chlorophyll content were significantly downregulated in the yellowed leaves of SJP26 transgenic N. benthamiana”
Claim · model-written summary
SJP26 transformation repressed chlorophyll biosynthesis gene expression in sour jujube calli, consistent with infected yellowed leaves.
Verbatim
e0“Transformation of SJP26 in sour jujube calli confirmed the repression of gene expression related to chlorophyll biosynthesis and chlorophyll content, which were consistent with those in JWB phytoplasma-infected yellowed leaves”
Claim · model-written summary
SJP26 transformation repressed chlorophyll content in sour jujube calli, consistent with infected yellowed leaves.
Verbatim
e0“Transformation of SJP26 in sour jujube calli confirmed the repression of gene expression related to chlorophyll biosynthesis and chlorophyll content, which were consistent with those in JWB phytoplasma-infected yellowed leaves”
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