Loss of function of the AP2/ERF transcription factor StGAME9 abolishes activation and induction of steroidal glycoalkaloid biosynthesis in potato plants.

Bifurcation of StCRY1-StHY5 axis orchestrates blue light-enhanced glycoalkaloid and chlorophyll accumulation in potato tubers.

Potato, the fourth largest food crop in the world, stores nutrients in underground tubers. However, light exposure induces tuber accumulation of chlorophyll and toxic steroidal glycoalkaloids (SGAs), an unwanted trait called tuber greening causes potato quality decline and parts of tuber inedible. Despite progress in enzymatic cascades governing SGAs biosynthesis, the regulatory scheme of SGAs and chlorophyll metabolism in light-exposed tubers persists as a critical knowledge gap. Here, we identify the blue light receptor StCRY1 plays a predominant role in light-induced tuber greening and SGAs elevation, which functions as a light-controlled transcriptional switch for genes involved in SGAs and chlorophyll biosynthesis. We show that transcription factor StHY5 acts downstream of StCRY1 to co-regulates both chlorophyll and SGAs metabolism. However, StMYB4, a transcription factor regulated by StHY5, promotes SGAs synthesis by directly binding to SGA biosynthetic genes without affecting chlorophyll homeostasis. Furthermore, StCRY1 employs a dual strategy by modulating StMYB4 expression and physically interaction with StMYB4 to regulate its transcriptional activity. Collectively, 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.

The PtARF6/PtARF8-PtGH3.1 transcriptional module regulates auxin homeostasis and dwarfism in citrus.

Dwarfing rootstocks are crucial for high-density and labor-efficient citrus cultivation, yet the molecular mechanisms underlying plant height regulation remain poorly understood. Using an integrated multi-omics analysis of dwarf and normal-height red tangerine (Citrus reticulata) × trifoliate orange (Poncirus trifoliata) hybrid seedlings, we identified the Gretchen Hagen 3.1 gene PtGH3.1, an auxin-conjugating enzyme, as an important regulator of dwarfism. Compared with normal-height hybrid seedlings, PtGH3.1 was significantly upregulated in the shoot tips of dwarf hybrid seedlings, correlating with reduced free auxin (indole-3-acetic acid, IAA) levels. Functional studies in a model citrus system (Citrus macrocarpa) demonstrated that heterologous overexpression of PtGH3.1 decreased free IAA and inhibited plant growth, whereas CRISPR/Cas9-mediated knockout of its homolog CmGH3.1 with editing ratio below 40% promoted growth. Mechanistically, the transcription factors auxin response factor 6 (PtARF6) and auxin response factor 8 (PtARF8) physically interact, forming a heterodimer that activates PtGH3.1 transcription. Dwarf hybrid seedlings exhibited elevated PtARF6 but reduced PtARF8 transcript levels. Heterologous overexpression of either PtARF6 or PtARF8 in Citrus macrocarpa induced dwarfism by activating CmGH3.1 expression. This study reveals a PtARF6/8-PtGH3.1 transcriptional module that regulates auxin homeostasis through IAA conjugation, providing genetic insights into GH3.1-mediated dwarfism and identifying precise targets (PtGH3.1, PtARF6, and PtARF8) for breeding dwarfing rootstocks in citrus.

MeJA-responsive MYB41-MYC2 cascade integrates glucomannan biosynthesis and DoTIP1–1 activation during salinity tolerance in Dendrobium officinale

Soil salinization limits the yield and quality of Dendrobium officinale. The molecular mechanisms linking methyl jasmonate (MeJA) signaling to the biosynthesis of glucomannans (GMs) under salinity remain unclear. In the WGCNA of MeJA- and salinity-treated D. officinale transcriptome, an R2R3-MYB transcription factor was identified, DoMYB41, which was highly expressed in stems and induced by both treatments. Overexpression of DoMYB41 in PLBs increased GMs and anthocyanin, enhanced the activities of antioxidant enzymes, reduced oxidative damage, and elevated relative water content, whereas CRISPR/Cas9 knockout lines showed opposite phenotypes. Transcriptomic analysis identified DoTIP1–1 as a key downstream target, and biochemical assays (dual-LUC, Y1H, EMSA) confirmed that DoMYB41 activates DoTIP1–1 transcription by directly targeting the MBS motif present in its promoter. Furthermore, DoMYB41 physically interacted with the bHLH transcription factor DoMYC2, which alone bound to and activated the promoters of both DoTIP1–1 and DoMYB41, forming a positive feedback loop. Intriguingly, DoMYB41 and DoMYC2 synergistically activated DoTIP1–1. These findings uncovered a MeJA-responsive DoMYB41-DoMYC2 cascade that iteratively activates DoTIP1–1 expression and promotes the biosynthesis of GMs, thereby enhancing salinity tolerance in D. officinale. This study also provides genetic targets for salinity tolerance in breeding programs for this horticultural orchid.

Loss-of-function of StFKF1 delays flowering and tuberization under long-day conditions in potato

Genomic characterization, expression and functional analysis of the plant homeodomain (PHD) family in tomato (Solanum lycopersicum L.) under abiotic stresses

Loss of the plastidial hexokinase CsHXK3 triggers metabolic starvation and ROS imbalance leading to pollen abortion in cucumber.

Male sterility is a vital trait for hybrid seed production. However, the synergistic coordination between sugar metabolism and reactive oxygen species (ROS) during pollen development remains poorly understood. Here, we identified a plastid-localized hexokinase, CsHXK3, that participates in both processes in cucumber (Cucumis sativus L.). CsHXK3 is localized to the tapetum, microspores, and vascular tissues of the anther. The significant downregulation of CsHXK3 expression in cell wall invertase 3-silenced (CsCWIN3-RNAi) lines supports its essential role in downstream hexose utilization. Biochemical analysis confirmed that CsHXK3 is a glucose-preferring enzyme that is essential for hexose phosphorylation. The CRISPR/Cas9-mediated knockout of CsHXK3 resulted in severe male sterility, characterized by defective tapetal programmed cell death, collapsed pollen grains, and severely impaired pollen germination. Loss of CsHXK3 led to reduced accumulation of sugars (glucose, fructose, and sucrose) and starch in the anthers, accompanied by substantially downregulated expression of sugar transporter genes, including Sugars Will Eventually be Exported Transporters (CsSWEETs) and Sugar Transport Protein 13 (CsSTP13). CsHXK3 deficiency disrupted ROS homeostasis by reducing hydrogen peroxide (H2O2) levels, which was accompanied by the downregulated expression of the ROS-generating gene Respiratory Burst Oxidase Homolog B (CsRBOHB) and upregulated expression of genes encoding ROS-scavenging peroxidases. Our findings indicate that CsHXK3 may coordinate carbohydrate metabolism with ROS homeostasis during pollen development, offering insights into the metabolic regulation of male reproductive success in plants.