SUMMARY KNOX (KNOTTED1‐like HOMEOBOX) transcription factors regulate the expression of genes involved in plant growth, development, and immunity by specifically binding to DNA elements. Previously, we found that the Phytophthora infestans RxLR effector Pi22798 targets the potato transcription factor StKNOX3 to promote colonization. We show here that StKNOX3 interacts with StHUB1 and StHUB2, two E3 ubiquitin ligases that monoubiquitinate histone 2B to form H2Bub1. StKNOX3 stabilizes StHUB1 and StHUB2 in the nucleus, and the StKNOX3‐StHUB1/2 complex acts to enhance P. infestans infection. The effector Pi22798 promotes the formation of the StKNOX3‐StHUB1/2 complex, facilitating the nuclear accumulation of StHUB1/2, thereby elevating H2Bub1 levels and increasing plant susceptibility. Combined ChIP‐Seq and RNA‐Seq analyses demonstrate that StKNOX3 modulates transcriptome reprogramming governing cell wall composition, phytohormone responses, and stress responses. StKNOX3 directly binds to the core motifs TGAC or TGTCA in promoter regions of target genes and represses the expression of multiple defense‐related genes. Expression of Pi22798 results in reinforced regulation of the StKNOX3‐targeted genes by affecting the binding affinity of StKNOX3 to their promoters and increasing H2Bub1 levels. Our data support a model in which the host StKNOX3‐StHUB1/2 complex is hijacked by Pi22798 to induce epigenetic modifications that ultimately enhance potato susceptibility to P. infestans.
Jing Zhou, Xiao-Shuang Zhou, Jia-Hui Nie et al.· The Plant Journal· 0 citations
Differential coloration of potato tuber skin is an important agronomic trait. However, its genetic regulatory mechanism remains unclear. In this study, an F₁ segregation population was constructed, and segregation in tuber skin coloration was observed. Using bulked segregant analysis by sequencing (BSA-seq) combined with fine mapping, a major quantitative trait locus (QTL) was mapped to a 52.24–53.08 Mb interval on Chr10. Within this region, StMYBA1, an R2R3-MYB transcription factor, emerged as the key candidate gene. Notably, a 6-bp (CTCCTC) deletion in the exon of StMYBA1 caused the loss of two proline residues, which was strongly associated with the absence of differential skin coloration. Further investigations demonstrated that overexpression of StMYBA1 markedly enhanced anthocyanin accumulation in both leaves and tubers. In transgenic lines, delphinidin content in leaves increased by 216.6%–297.4%, and after five days of light exposure, tuber eyes and heels exhibited a pronounced purple pigmentation. Consistently, key anthocyanin biosynthetic genes, including StANS and StF3′H, were significantly upregulated. Dual-luciferase assays further confirmed that StMYBA1 promotes anthocyanin biosynthesis by activating the MYB transcription factor StAN2 and its downstream targets. Importantly, the 6-bp deletion partially attenuated StMYBA1 regulatory activity, as reflected by reduced activation of several anthocyanin-related promoters and moderately lower anthocyanin accumulation in transient assays, while DNA-binding activity was retained. Collectively, these findings provide new insights into the regulatory role of StMYBA1 in potato anthocyanin biosynthesis and identify a potentially useful genetic target for potato quality improvement.
Xi-Juan Zhao, Chen-Xi Li, Sheng-Xuan Liu et al.· Horticulture Research· 0 citations
A previously unrecognized AAA+ ATPase–F-box module that controls receptor homeostasis is revealed and StGCN4 is identified as a promising molecular target for breeding high-yielding and late blight resistant potato cultivars.
These findings uncover a modularly coordinated control of SGAs accumulation and chlorophyll biosynthesis by bifurcation of StCRY1-StHY5 axis, providing a promising strategy to concurrently curb light-induced tuber greening and glycoalkaloids accumulation.
Jun Qin, S. Jing, Shengxuan Liu et al.· The Plant Cell· 0 citations
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