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

Heterologous Expression of the Plastid Glycerolipid Acyltransferase AtATS1 Negatively Regulates Salt Stress Tolerance in Rapeseed (Brassica napus)

Plastid-localized glycerol‑3‑phosphate acyltransferase (ATS1) catalyzes the initial acylation step in the prokaryotic branch of glycerolipid biosynthesis and is pivotal for membrane lipid remodeling. In this study, we investigated the role of Arabidopsis thaliana ATS1 (AtATS1) in salt tolerance using transgenic Brassica napus lines overexpressing AtATS1 and wild-type plants. Under 150 mM salt stress, AtATS1-overexpressing lines exhibited significantly compromised tolerance, characterized by severe growth inhibition and cotyledon abscission compared to wild-type plants. Physiological assays further revealed that despite a hyper-induction of antioxidant enzymes (SOD and POD), the transgenic lines suffered from excessive reactive oxygen species (ROS) accumulation and elevated malondialdehyde (MDA) levels, indicating a failure to maintain redox homeostasis. Transcriptomic analysis demonstrated that AtATS1 overexpression disrupts the stress response by misallocating metabolic resources toward glucosinolate biosynthesis and constitutively repressing the MAPK signaling cascade (including WRKY42, MPK15, and MEKK1). In conclusion, these findings identify AtATS1 as a negative regulator of salt tolerance in B. napus. This study provides new insights into the link between lipid metabolism and abiotic stress responses and highlights the need for careful modulation of glycerolipid biosynthesis when engineering salt-resilient rapeseed varieties.

The OsMYB103-OsGLOX5 module regulates tapetum degradation and male fertility in rice.

Anther tapetum degradation is essential for normal pollen formation in rice, yet the underlying regulatory network remains poorly understood. We isolated a novel male sterility rice mutant, osglox5, and confirmed that the target gene LOC_Os11g06870 encodes a glyoxal/galactose oxidase protein with both glyoxal oxidase (GLOX) and galactose oxidase (GAO) activities and is required for hydrogen peroxide (H2O2) production in anthers. Insufficient H2O2 content in osglox5 anthers causes delayed tapetum degradation and defective pollen wall formation, resulting in pollen abortion. OsGLOX5 is highly expressed during stage 9 of anther development, specifically in microspores and tapetum, and localizes to the endoplasmic reticulum. The tapetum-specific transcription factor OsMYB103 directly binds the OsGLOX5 promoter and activates its expression. This study provides the first evidence that a protein with both glyoxal oxidase and galactose oxidase activities plays an essential role in rice tapetum degradation, and identifies a novel MYBs-GLOXs regulatory axis, advancing our understanding of the tapetum degradation network.

Plastid G6PD3 and cytosolic G6PD5/6 are involved in the Ustilago sp. HFJ311-enhanced tolerance to cadmium stress in Arabidopsis.

BACKGROUND Cadmium (Cd) contamination in soils severely threatens agricultural security and productivity. Glucose-6-phosphate dehydrogenase (G6PD), a key rate-limiting enzyme in the pentose phosphate pathway, is crucial for plant growth and stress tolerance. The endophytic fungus Ustilago sp. HFJ311 enhances plant Cd tolerance, but the underlying mechanism, especially the regulatory roles of G6PD in this process, remains unclear. RESULTS Here, we demonstrate that plastid G6PD3 and cytosolic G6PD5/G6PD6 synergistically govern the HFJ311-induced Cd tolerance in Arabidopsis. HFJ311 significantly enhanced seedling biomass, leaf area, stomatal density, and photosynthetic pigment content in wild type (Col-0) under control and Cd treatment conditions. Comparatively, compared with Col-0, the shoot fresh weight (FW) of g6pd5 and g6pd6 and the root FW of g6pd3 were significantly reduced under Cd+HFJ311 conditions. Under Cd stress, all the growth-promoting effects of HFJ311 were further attenuated in g6pd3/5/6 triple mutants. Mechanistically, HFJ311 up-regulated G6PD3/5/6 expressions, maintained nicotinamide adenine dinucleotide phosphate (NADPH) homeostasis, and enhanced antioxidant enzyme activities and ascorbate-glutathione (ASA-Glu) cycle efficiency to mitigate reactive oxygen species (ROS) burst and oxidative damage. Meanwhile, HFJ311 down-regulated the expression of Cd transporter genes (Iron-Regulated Transporter 1, IRT1; ZRT/IRT-like proteins, ZIPs; NATURAL RESISTANCE-ASSOCIATED MACROPHAGE PROTEIN 3/4, NRAMP3/4), ultimately reducing Cd transport from roots to shoots. The redox balance in the g6pd3/5/6 mutant was disrupted, thus aggravated Cd translocation and triggered a nitric oxide (NO) overproduction. However, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), a NO scavenger, completely abolished the protective effects of HFJ311 under Cd stress, indicating that NO is involved in growth-promoting effect of HFJ311. CONCLUSION Collectively, our findings uncover a novel mechanism whereby G6PD3/5/6 act as central hubs mainly integrating redox homeostasis, Cd transport and chelation to mediate endophyte-enhanced Cd tolerance.

Heterologous Expression of CsAlaDC Enhances Thermotolerance through a Functional Ethylamine-Theanine-GABA Metabolic Network in Tomato.

Heterologous expression of CsAlaDC establishes a functional ethylamine-theanine metabolic branch in tomato and enhances thermotolerance through coordination with the GABA metabolic network, offering a promising strategy to improve both stress resilience and nutritional quality in crops.

Characterization of Nucleobase Cation Symporter 1 (NCS1) Localized to the Plastids of Nicotiana tabacum.

Jasmonate-mediated defense responses redirect plant resources from growth to defense, imposing significant demands on the nitrogen economy to produce nitrogenous compounds, such as alkaloids. However, the mechanisms by which plants maintain essential central metabolic processes, such as nucleotide synthesis, under nitrogen resource competition remain unclear. Therefore, in this study, we characterized the nucleobase cation symporter NtNCS1 in Nicotiana tabacum. Notably, NtNCS1 mRNA exhibited opposing organ-specific regulation by jasmonic acid, with induction in roots (the site of nicotine synthesis) but repression in leaves. NtNCS1 was localized to the plastid envelope in metabolically active cells, including mesophyll, phloem-associated, and, notably, guard cells. This dual regulation suggests that NtNCS1 plays a key role in reallocating nitrogen resources. In roots, its expression possibly contributes to maintaining the essential nucleotide pools for basal metabolism when nitrogen is diverted to alkaloid production. Conversely, its repression in leaves possibly conserves nitrogen by downregulating growth, thereby reallocating resources to defense. Overall, this study highlights the potential roles of NCS1 transporters in safeguarding central metabolism and mediating the plant growth-defense trade-off.

Down-regulation of VvPLL3 enhances grapevine resistance to Erysiphe necator via defense activation and cell wall remodeling.