Pinellia ternata is an important traditional Chinese medicinal plant. The growth of P. ternata is sensitive to high temperatures. To gain a better understanding of heat stress responses in P. ternata, we performed a comparative proteomic analysis. P. ternata seedlings were subjected to a temperature of 38 °C and samples were collected 24 h after treatment. Increased relative ion leakage and lipid peroxidation suggested that oxidative stress was frequently generated in rice leaves exposed to high temperature. Two-dimensional electrophoresis (2-DE) was used to analyze heat-responsive proteins. More than 600 protein spots were reproducibly detected on each gel; of these spots, 20 were up-regulated, and 7 were down-regulated. A total of 24 proteins and protein species were successfully identified by MALDI-TOF/TOF MS. These proteins and protein species were found to be primarily small heat shock proteins (58%) as well as proteins involved in RNA processing (17%), photosynthesis (13%), chlorophyll biosynthetic processes (4%), protein degradation (4%) and defense (4%). Using 2-DE Western blot analysis, we confirmed the identities of the cytosolic class II small heat shock protein (sHSPs-CII) identified by MS. The expression levels of four different proteins [cytosolic class I small heat shock protein (sHSPs-CI), sHSPs-CII, mitochondrial small heat shock protein (sHSPs-MIT), glycine-rich RNA-binding protein (GRP)] were analyzed at the transcriptional level by quantitative real-time PCR. The mRNA levels of three sHSPs correlated with the corresponding protein levels. However, GRP was down-regulated at the beginning of heat stress but then increased substantially to reach a peak after 24 h of heat stress. Our study provides valuable new insight into the responses of P. ternata to heat stress.

Prunella vulgaris L. (Labiatae) contains a variety of structurally diverse natural products, primarily rosmarinic acid (RA), ursolic acid (UA) and oleanolic acid (OA), which possess a wide array of biological properties. In the present study, P. vulgaris was harvested at three developmental stages (vegetative, full-flowering and mature-fruiting stages), dissected into stem and leaf tissues and assayed for chemical contents using high performance liquid chromatography. Significant changes in the concentrations of the major secondary metabolites (RA, UA and OA) were observed at the different development stages. The highest concentrations of RA, UA and OA were found at the full-flowering stage (15.83 mg/g dry weight (DW) RA, 1.77 mg/g DW UA and 0.65 mg/g DW OA). Among the different aerial parts of the plant, the concentrations of RA, UA and OA were higher in the leaves than in the stems at the different developmental stages. These results suggest that the full-flowering stage is characterized by the highest concentrations of bioactive compounds. Therefore, this stage may be the optimum point for harvesting P. vulgaris plants. In additional, the leaves of P. vulgaris demonstrated higher RA, UA and OA concentrations than the stems, suggesting higher utilization potential.

Prunella vulgaris L. is a medical plant cultivated in sloping, sun-shaded areas in China. Recently, owing to air-environmental stress, especially drought stress strongly inhibits plant growth and development, the appropriate fertilizer supply can alleviate these effects. However, these is little information about their effects on P. vulgaris growing in arid and semi-arid areas with limited water and fertilizer supply. In this study, water stress decreased the photosynthetic pigment contents, inhibited photosynthetic efficiency, induced photodamage in photosystem 2 (PS2), and decreased leaf instantaneous WUE (WUEi). The decreased net photosynthetic rate (Pn) under medium drought stress compared with the control might result from stomatal limitations. However, fertilizer supply improved photosynthetic capacity by increasing the photosynthetic pigment contents and enhancing photosynthetic efficiency under water deficit. Moreover, medium fertilization also increased WUEi under the two water conditions, but fertilizer supply did little to alleviate the PS2 photodamage caused by drought stress. Hence, drought stress was the primary limitation in the photosynthetic process of P. vulgaris seedlings, while the photosynthetic characteristics of the seedlings exhibited positive responses to fertilizer supply. Appropriate fertilizer supply is recommended to improve photosynthetic efficiency, enhance WUEi and alleviate photodamage under drought stress.