Comparison of the Ability to Control Water Loss in the Detached Leaves of Wedelia trilobata, Wedelia chinensis, and Their Hybrid

Heat Wave Adaptations: Unraveling the Competitive Dynamics Between Invasive Wedelia trilobata and Native Wedelia chinensis

Heat waves (HW) are projected to become more frequent and intense with climate change, potentially enhancing the invasiveness of certain plant species. This study aims to compare the physiological and photosynthetic responses of the invasive Wedelia trilobata and its native congener Wedelia chinensis under simulated heat wave conditions (40.1 °C, derived from local historical data). Results show that W. trilobata maintained higher photosynthetic efficiency, water-use efficiency (WUE), and total biomass under HW, suggesting that its ability to optimize above-ground growth contributes to its success in heat-prone environments. In contrast, W. chinensis focused more on root development and antioxidant protection, exhibiting a decrease in total biomass under heat wave conditions. These results indicate that W. trilobata employs a more effective strategy to cope with heat stress, likely enhancing its competitive advantage in regions affected by heat waves. This study highlights the importance of understanding species-specific responses to extreme climate events and underscores the potential for heat waves to drive ecological shifts, favoring invasive species with higher phenotypic plasticity.

Adaptation of the Invasive Plant Sphagneticola trilobata (L.) Pruski to Drought Stress

Invasive species and their hybrids with native species threaten biodiversity. However, there are few reports on the drought stress adaptability of invasive species Sphagneticola trilobata (L.) Pruski and its hybrid with native species S. calendulacea. In this study, relative water content (RWC), abscisic acid (ABA), reactive oxygen species, antioxidant capacity, and photosynthetic capacity were measured in the hybrid and its parents under drought stress (13% PEG-6000). Under drought stress, the ABA content and RWC in S. trilobata were the highest. RWC decreased by 28% in S. trilobata, 41% in S. calendulacea, and 33% in the hybrid. Activities of the antioxidant enzymes in S. trilobata were the highest, and the accumulation of malondialdehyde (MDA) was the lowest (4.3 μg g-1), while it was the highest in S. calendulacea (6.9 μg g-1). The maximum photochemical efficiency (Fv/Fm) of S. calendulacea was the lowest (0.71), and it was the highest in S. trilobata (7.5) at 8 h under drought stress. The results suggest that the drought resistance of the hybrid was weaker than that of S. trilobata but stronger than that of S. calendulacea. Therefore, the survival of S. calendulacea may be threatened by both the invasive species S. trilobata and the hybrid.

Adaptation of the Invasive Plant Sphagneticola trilobata to Flooding Stress by Hybridization with Native Relatives

Hybridization is common between invasive and native species and may produce more adaptive hybrids. The hybrid (Sphagneticola × guangdongensis) of Sphagneticola trilobata (an invasive species) and S. calendulacea (a native species) was found in South China. In this study, S. trilobata, S. calendulacea, and Sphagneticola × guangdongensis were used as research materials to explore their adaptability to flooding stress. Under flooding stress, the ethylene content and the expression of key enzyme genes related to ethylene synthesis in Sphagneticola × guangdongensis and S. calendulacea were significantly higher than those in S. trilobata. A large number of adventitious roots and aerenchyma were generated in Sphagneticola × guangdongensis and S. calendulacea. The contents of reactive oxygen species and malondialdehyde in Sphagneticola × guangdongensis and S. calendulacea were lower than those in S. trilobata, and the leaves of S. trilobata were the most severely damaged under flooding stress. The results indicate that hybridization catalyzed the tolerance of Sphagneticola × guangdongensis to flooding stress, and the responses of Sphagneticola × guangdongensis to flooding stress were more similar to that of its native parent. This suggests that hybridization with native relatives is an important way for invasive species to overcome environmental pressure and achieve invasion.

The SPL transcription factor TaSPL6 negatively regulates drought stress response in wheat

Environmental stresses, such as heat and drought, severely affect plant growth and development, and reduce wheat yield and quality globally. Squamosa promoter binding protein-like (SPL) proteins are plant-specific transcription factors that play a critical role in regulating plant responses to diverse stresses. In this study, we cloned and characterized TaSPL6, a wheat orthologous gene of rice OsSPL6. Three TaSPL6 homoeologs are located on the long arms of chromosomes 4A, 5B, and 5D, respectively, and share more than 98% sequence identity with each other. The TaSPL6 genes were preferentially expressed in roots, and their expression levels were downregulated in wheat seedlings subjected to heat, dehydration, and abscisic acid treatments. Subcellular localization experiments showed that TaSPL6 was localized in the nucleus. Overexpression of TaSPL6-A in wheat resulted in enhanced sensitivity to drought stress. The transgenic lines exhibited higher leaf water loss, malondialdehyde and reactive oxygen species (ROS) content, and lower antioxidant enzyme activities after drought treatment than wild-type plants. Gene silencing of TaSPL6 enhanced the drought tolerance of wheat, as reflected by better growth status. Additionally, RNA-seq and qRT-PCR analyses revealed that TaSPL6-A functions by decreasing the expression of a number of genes involved in stress responses. These findings suggest that TaSPL6 acts as a negative regulator of drought stress responses in plants, which may have major implications for understanding and enhancing crop tolerance to environmental stresses.

Comparative genetic and epigenetic of the Sphagneticola trilobata (L.) Pruski from different regions in China

BACKGROUND

Sphagneticola trilobata (L.) Pruski is a prevalent and widely distributed invasive plant in South China. To investigate the molecular mechanisms underlying its rapid adaptation, we employed DNA methylation-sensitive amplified polymorphism (MSAP) and simple sequence repeat (SSR) analysis to study 60 S. trilobata individuals collected from Fuzhou (FZ), Haikou (HK), Jinghong (JH) and Guangzhou (GZ).

RESULTS

In this study, we computed the Shannon diversity index (I) of SSR and MSAP as 0.354 and 0.303, respectively. The UPGMA phylogenetic tree and PCoA analyses showed that MSAP had a better discriminatory power to distinguish populations from different regions. Notably, the GZ population was found to be the most distinct from the other three populations. Moreover, Mantel analysis revealed a significantly higher correlation between epigenetic distance and geographic distance as compared to genetic distance and geographic distance. Consequently, the correlation between epigenetic distance and geographic distance observed to be markedly stronger than that between genetic distance and geographical distance on Mantel analysis.

CONCLUSIONS

The S. trilobata populations in various regions displayed a high of complementary genetic and epigenetic diversity, which was a key feature contributing to their rapid invasion. Interestingly, the correlation between epigenetics and geographical distance was significantly stronger than that observed for genetics and geographical distance. These findings indicated that the epigenetic mechanism of S. trilobar exhibited high plasticity, leading to significant differences in methylation pattern across different populations.

Adaptive photosynthetic strategies of the invasive plant Sphagneticola trilobata and its hybrid to a low-light environment

In stressful environments, invasive plants acclimate more efficiently than native plants and hybridization mainly contributes to this process. We examined changes in the morphological characteristics, photosynthetic characteristics, and antioxidant capacity of Sphagneticola trilobata and its hybrids in a low-light environment to explore their invasiveness, with Sphagneticola calendulacea serving as the control. The morphological plasticity of S. trilobata was not dominant, the maximal photochemical efficiency of PSII, actual quantum yield of PSII, and electron transport rate of PSII increased and nonphotochemical quenching decreased, while S. calendulacea and the hybrid produced opposite results. S. trilobata showed fewer spots stained for reactive oxygen species in tissues, with an increase in superoxide dismutase activity. Although S. trilobata is a heliophilous plant, we found that the shade tolerance of S. trilobata and the hybrid were stronger than that of S. calendulacea, which may be one important mechanism of invasion.

Adaptation of the Invasive Plant (Sphagneticola trilobata L. Pruski) to a High Cadmium Environment by Hybridizing With Native Relatives

Invasive species can evolve rapidly in the invasion areas to adapt to new habitats. Sphagneticola trilobata L. Pruski, an invasive species, was studied for its tolerance to cadmium (Cd) in the soil and compared with its natural hybrid. From the perspective of photosynthetic physiology, antioxidant characteristics, and leaf hormone levels, the differences between the leaves of the two species before and after Cd treatment were compared. The results showed that the hybrid had stronger tolerance to Cd stress than invasive species. After Cd stress, the indexes of gas-exchange [net photosynthetic rate (Pn), intercellular CO₂ concentration (Ci), stomatal conductance (Gs), and transpiration rate (Tr)] of the hybrid was higher than invasive species, while the content of non-enzymatic antioxidants (flavonoids and total phenols) and antioxidant enzyme activities [peroxidase (POD) and superoxide dismutase (SOD)] was lower in hybrid than in invasive species. The changes in the content of plant hormones [auxin (IAA) and abscisic acid (ABA)] under Cd stress showed that hybrid can still maintain growth and prevent leaf senescence. Furthermore, the differences in gene expression between hybrid and invasive species in photosynthetic physiology, the antioxidant capacity of leaves, and endogenous hormone (IAA and ABA) synthesis pathway also showed that hybrid has stronger Cd tolerance than invasive species. This suggests that invasive species will realize the invasion through hybridization with the native relatives to overcome the stress from environmental factors. The study implied that hybridization between invasive species and native relatives is an important way for invasive species to spread in a wider and new environment that invasive species have not experienced in the area of origin.