Foliar methyl jasmonate (MeJA) application increased 2-acetyl-1-Pyrroline (2-AP) content and modulated antioxidant attributes and yield formation in fragrant rice

Methyl Jasmonate (MeJA) Promotes the Self-Pollen Tube Growth of Camellia oleifera by Regulating Lignin Biosynthesis

Self-incompatibility (SI) poses a significant reproductive barrier, severely impacting the yield, quality, and economic value of Camellia oleifera. In this study, methyl jasmonate (MeJA) was employed as an exogenous stimulus to alleviate SI in C. oleifera. The research findings revealed that an exogenous dose of 1000 μmol·L-1 MeJA enhanced the germination and tube growth of C. oleifera self-pollen and greatly improved ovule penetration (18.75%) and fertilization (15.81%), ultimately increasing fruit setting (18.67%). It was discovered by transcriptome analysis that the key genes (CAD, C4H) involved in the lignin production process exhibited elevated expression levels in self-pistils treated with MeJA. Further analysis showed that the lignin concentration in the MeJA-treated pistils was 31.70% higher compared with the control group. As verified by pollen germination assays in vitro, lignin in the appropriate concentration range could promote pollen tube growth. Gene expression network analysis indicated that transcription factor bHLH may be pivotal in regulating lignin biosynthesis in response to MeJA, which in turn affects pollen tubes. Further transient knockdown of bHLH (Co_33962) confirmed its important role in C. oleifera pollen tube growth. In summary, the application of MeJA resulted in the stimulation of self-pollen tube elongation and enhanced fruit setting in C. oleifera, which could be associated with the differential change in genes related to lignin synthesis and the increased lignin content.

Transcriptome analysis of the coexpression network of genes related to antioxidant characteristics after grain filling in purple rice

Antioxidant capacity is an important indicator for evaluating the growth and developmental quality of rice. This study has guiding significance for the cultivation of high-nutrient-value varieties. To investigate the molecular mechanisms underlying the antioxidant characteristics of rice grains after the filling stage, Yangzinuo 1 (YZN1) was used as the experimental material, and grains collected at five different time points (7 days apart) after the filling stage were used for transcriptome sequencing. Through weighted gene coexpression network analysis (WGCNA), a coexpression network of gene weights related to antioxidant characteristics was constructed. LOC_Os10g39140, LOC_Os10g38276, and LOC_Os05g45740 were identified from the 2 modules showing the highest correlations with the target traits. GO functional annotation showed that target modules were enriched in pathways related to phenylalanine, flavonoids, and other related pathways, such as GO:0006558, GO:0006559, GO:0009812, and GO:0009813. Correlation analysis with metabolites revealed that differentially expressed genes were significantly enriched in pathways related to antioxidant characteristics and energy metabolism processes, such as glycolysis/gluconeogenesis and flavonoid biosynthesis. The core genes identified in this study were found to be highly correlated with antioxidant characteristics and enriched in pathways related to metabolic and energy pathways and molecular activities. These results provide an effective dataset supporting breeding targeting functional rice characteristics.

Riboflavin improves grain yield, 2-acetyl-1-pyrroline accumulation, and antioxidative properties of fragrant rice

BACKGROUND

Riboflavin, a vital water-soluble vitamin with antioxidative activity, plays a critical role in maintaining overall bodily health and defense responses. However, its impact on fragrant rice yield and aroma remains unexplored.

RESULTS

In a 2022 pot experiment with Meixiangzhan and Yuxiangyouzhan fragrant rice cultivars, we applied riboflavin foliar treatments at concentrations of 0 (CK), 10 (R10), 20 (R20), and 40 (R40) mg L-1 during the initial heading stage. Riboflavin increased rice yield, 2-acetyl-1-pyrroline (2-AP) content, and antioxidative properties. It boosted 2-AP level by 13.1-50.1% for Meixiangzhan and 22.3-35.3% for Yuxiangyouzhan, with the highest levels in R20 and R10 treatments. This increase is significantly correlated with elevated levels of proline, pyrroline-5-carboxylic acid, pyrroline, and methylglyoxal, as well as heightened enzyme activities, including those of proline dehydrogenase, ornithine aminotransferase, and pyrroline-5-carboxylic acid synthetase (P5CS). The R20 treatment resulted in the highest yield due to an improved seed-setting rate. Importantly, a positive correlation emerged between 2-AP content and yield, both significantly linked to superoxide dismutase, proline, hydrogen peroxide, P5CS, catalase, and pyrroline.

CONCLUSION

Riboflavin maintained enzyme activities, regulated substance synthesis pathways, and increased 2-AP and yield, especially in the R20 treatment. These insights advance fragrant rice production theory by uncovering riboflavin's role in the development of fragrant rice. © 2023 Society of Chemical Industry.

Effects of paclobutrazol seed priming on seedling quality, photosynthesis, and physiological characteristics of fragrant rice

BACKGROUND

Paclobutrazol is widely used in the agricultural field. This study investigated the effects of seed priming with different concentrations of paclobutrazol on seedling quality, 2-acetyl-1-pyrroline (2-AP, a key aroma component of fragrant rice) biosynthesis, and related physiological and biochemical indicators in fragrant rice seedlings.

RESULTS

The experiment is being conducted at the College of Agriculture, South China Agricultural University. In the experiment, three concentrations of paclobutrazol (Pac 1: 20 mg·L-1; Pac 2: 40 mg·L-1; Pac 3: 80 mg·L-1) were used to initiate the treatment of fragrant rice seeds, while water treatment was used as a control (CK). The results showed that compared with CK, paclobutrazol treatment reduced plant height, increased stem diameter, and increased fresh and dry weight of aromatic rice seedlings. Moreover, paclobutrazol treatment also increased the seedlings' photosynthetic pigment content and net photosynthetic rate.

CONCLUSIONS

This study demonstrates that paclobutrazol primarily increases the content of proline by reducing the content of glutamate and down-regulating the expression of P5CS2, thereby promoting the conversion of proline to the aromatic substance 2-AP. Under the appropriate concentration of paclobutrazol (40 mg·L-1~80 mg·L-1), the seedling quality, stress resistance, and aroma of fragrant rice can be improved.

Water-saving techniques: physiological responses and regulatory mechanisms of crops

Water-saving irrigation techniques play a crucial role in addressing water scarcity challenges and promoting sustainable agriculture. However, the selection of appropriate water-saving irrigation methods remains a challenge in agricultural production. Additionally, the molecular regulatory mechanisms of crops under water-saving irrigation are not yet clear. This review summarizes the latest research developments in the application of different water-saving irrigation technologies to five important crops (rice, wheat, soybeans, maize, and cotton). It provides an overview of the impact of different irrigation techniques on crop yield, water use efficiency (WUE), physiology, growth, and environmental effects. Additionally, the review compares and contrasts the molecular regulatory mechanisms of crops under water-saving irrigation techniques with those under traditional drought stress, emphasizing the significance of combining irrigation technologies with genetic engineering for developing drought-resistant varieties and improving WUE. Furthermore, the integration of various technologies can stimulate new management strategies, optimize water resource utilization, and enhance sustainability, representing a major focus for future research. In conclusion, this review underscores the importance of water-saving irrigation technologies, especially when combined with genetic engineering, in addressing water resource scarcity, increasing crop yields, and promoting sustainable agriculture.