Plant Physiology

Peng, Leilei; Xiao, Haijun; Xu, Yanghong; Huang, Zhihao; Yang, Xuan; Lv, Chen; Huang, Linghui; Hu, Jun

doi: 10.1093/plphys/kiaf187pmid: 40331370

The RNA-binding proteins (RBPs) encoded by the nucleus are essential for RNA metabolism in eukaryotes. Pentatricopeptide repeat (PPR) proteins, a large subset of RBPs, are essential for plant development and reproduction by participating in organellar RNA processing. Here, we identified an E-type PPR protein, PPR767, which functions in mitochondria. Knocking out PPR767 resulted in decreased plant height, thinner stems, shorter and narrower blades, and consequently affected yield traits compared with those of the wild-type. PPR767 primarily participated in the RNA editing of 4 sites related to NADH dehydrogenase (Nad), including nad1-674, nad3-155, nad3-172, and nad7-317. PPR767 interacted with multiple organellar RNA editing factors (MORFs), including MORF1 and MORF8, suggesting that the editosome in rice (Oryza sativa) is complex. The mutants showed decreased mitochondrial complex I activity and compromised mitochondrial structure. Furthermore, mutation of PPR767 influenced rice drought tolerance and the expression levels of genes involved in reactive oxygen species (ROS) accumulation. Therefore, PPR767 is essential for complex I activity by properly regulating the RNA editing efficiency of mitochondrial genes and affects drought tolerance by modulating ROS content in rice. Our findings provide valuable insights into the mechanisms by which PPRs fulfill their functions.

Gawande, Nilesh D

doi: 10.1093/plphys/kiaf323pmid: 40694610

Jené, Laia; Munné-Bosch, Sergi

doi: 10.1093/plphys/kiaf185pmid: 40329863

The evolution of parasitic plants has been marked by a progressive relaxation of selective pressures associated with maintaining photosynthesis, resulting in a wide diversity in photosynthetic capacity within this group. In this study, we explored this diversity by examining several hemi- and holoparasitic plants, focusing on photoprotection. Our findings revealed a strongly conserved evolutionary association between vitamin E, PSII activity, and chlorophyll content in parasitic plants, with α-tocopherol consistently being identified as the predominant vitamin E form. To validate the antioxidant and photoprotective role of α-tocopherol in a plant with reduced photosynthetic capacity, we investigated the interaction between the stem holoparasitic plant field dodder (Cuscuta campestris Yunck.), which retains partial PSII activity and low chlorophyll levels, and its host, lentil plant (Lens culinaris Medik). This protective role, essential for controlling lipid peroxidation within chloroplasts, was demonstrated both in planta and in isolated chloroplasts from field dodder exposed to photoinhibitory conditions induced by the synthetic photosensitizer Rose Bengal and light. Notably, our findings highlight the final evolutionary step in the conserved role of vitamin E in photosynthesis and photoprotection as revealed through parasitic plants.

Ma, Li; Zhang, Ziran; Liu, Mengli; Wang, Zhe; Zhang, Xinghua; Guo, Xinyang; Zhang, Jingyi; Hu, Junjie; Zhu, Wanchao; Li, Qing; Xu, Shutu; Xue, Jiquan

doi: 10.1093/plphys/kiaf299pmid: 40627785

Rising global temperatures present a substantial threat to crop production. Autophagy is an important catabolic process that promotes plant survival under stress, and AuTophaGy-related 8 (ATG8) proteins play key roles in plant autophagy, although the contributions of specific ATG8 isoforms to heat tolerance remain to be clarified. Here, we demonstrate that heat-induced expression of ZmATG8c promotes maize (Zea mays L.) thermotolerance during both vegetative and reproductive growth stages. ZmATG8c-knockout mutants showed lower seedling survival and grain yield under heat stress, whereas plants overexpressing ZmATG8c exhibited enhanced seedling survival and improved yield, which were attributable to greater autophagosome production, elevated levels of ATG8, and reduced accumulation of ubiquitinated protein aggregates. We also found that the heat-induced bZIP transcription factor ZmGBF1 could bind directly to the promoter of ZmATG8c and facilitate its expression. Maize gbf1 mutants showed significant inhibition of ZmATG8c thermal induction and increased sensitivity to heat stress. Our findings demonstrate that ZmATG8c and ZmGBF1 have a role in mediating thermotolerance, providing promising targets for engineering maize with improved resilience to thermal stress.

doi: 10.1093/plphys/kiaf089pmid: 40991310

Lee, Jae-Hyung; Doan, Thu Minh; Bruzual, Abigail; Senthilkumar, Sandhya; Yoo, Chan Yul

doi: 10.1093/plphys/kiaf289pmid: 40587430

Interorganellar communication is essential for maintaining cellular and organellar functions and adapting to dynamic environmental changes in eukaryotic cells. In angiosperms, light initiates photomorphogenesis, a developmental program characterized by chloroplast biogenesis and inhibition of hypocotyl elongation, through photoreceptors such as the red-/far-red-sensing phytochromes and their downstream signaling pathways. However, the mechanisms underlying nucleus–chloroplast crosstalk during photomorphogenesis remain elusive. Here, we show that light-regulated dual-targeting of NUCLEAR CONTROL OF PEP ACTIVITY (NCP) mediates bidirectional communication between the nucleus and chloroplasts via alternative promoter selection and retrograde translocation. Light promotes transcription from an upstream canonical transcription start site, producing a long NCP (NCP-L) isoform containing an N-terminal chloroplast transit peptide that directs chloroplast localization. In contrast, darkness or low red light conditions favor transcription from a downstream alternative start site, producing a shorter cytoplasmic isoform (NCP-S) that is rapidly degraded via the 26S proteasome. This light-regulated alternative transcription initiation depends on PHYTOCHROME-INTERACTING FACTORS (PIFs), key repressors of photomorphogenesis. Upon chloroplast import, NCP-L is processed into its mature form (NCPm), which promotes assembly and nucleoid localization of the plastid-encoded RNA polymerase (PEP) complex to initiate chloroplast biogenesis. Notably, NCP's nuclear function requires its prior localization to chloroplasts, supporting a model in which NCP mediates chloroplast-to-nucleus retrograde signaling. Consistent with this, NCP promotes stromule formation in Arabidopsis (Arabidopsis thaliana) hypocotyls, linking chloroplast dynamics to phytochrome-dependent nuclear pathways that restrict hypocotyl elongation. Our findings uncover an interorganellar communication mechanism in which light-dependent alternative promoter usage and retrotranslocation regulate photomorphogenesis, integrating nuclear and plastid signals to coordinate organ-specific developmental programs.

Musialak-Lange, Magdalena; Fiddeke, Katharina; Franke, Annika; Kragler, Friedrich; Abel, Christin; Wahl, Vanessa

doi: 10.1093/plphys/kiaf300pmid: 40638795

A plant's stem cell population in the shoot apical meristem (SAM) is maintained by WUSCHEL (WUS) and CLAVATA3 (CLV3). SAM size is dynamic and undergoes a more than 2-fold expansion upon transition to reproductive growth. The mechanism controlling this doming is largely unknown; however, coinciding increased trehalose 6-phosphate (T6P) levels suggest a participation of the T6P pathway in Arabidopsis (Arabidopsis thaliana). Moreover, lines misexpressing or with reduced expression of TREHALOSE PHOSPHATE SYNTHASE1 (TPS1) have smaller and larger SAMs, respectively. Here, we show that TREHALOSE PHOSPHATE PHOSPHATASEJ (TPPJ) is directly regulated by WUS. Changing TPPJ transcript levels in the outer layer affects SAM size and flowering time, and its reduction in the late-flowering clv3 mutant restores wild-type flowering. This is associated with altered mature microRNA156 abundance and expression of the SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE genes SPL3, SPL4, SPL5, and SPL9. Furthermore, SPL4 is controlled by WUS, while SPL4 directly represses WUS, establishing negative feedback regulation. This feedback loop is important for age pathway-induced flowering involving the T6P pathway and suggests dynamic feedback regulations between central meristem maintenance and flowering time regulators with sugar signaling throughout development.

Flores-Tornero, María

doi: 10.1093/plphys/kiaf201pmid: 40408272

Zhu, Sanming; Fu, Rao; Martin, Cathie; Zhao, Qing; Zhang, Yang

doi: 10.1093/plphys/kiaf356pmid: 40795392

Plants synthesize a diverse array of flavonoids that endow them with the ability to adapt to a wide range of natural environments. For humans, flavonoids have been used for centuries for their dietary health benefits and therapeutic applications. As a result, research into the biosynthesis, regulation, and metabolic engineering of flavonoids has received increasing attention. In this review, we present the latest advances in this field, with a particular focus on species-specific flavonoid biosynthetic pathways and newly discovered transcriptional regulatory mechanisms. Furthermore, we provide an overview of valuable flavonoids that have been synthesized successfully using metabolic engineering. The development of purple tomatoes is highlighted as a case study, demonstrating the potential to translate plant research into marketable high-flavonoid products.