Transcriptomic and physiological analyses of Symphytum officinale L. in response to multiple heavy metal stress.

Soil heavy metal contamination has become a global environmental issue, which threaten soil quality, food security and human health. Symphytum officinale L. have exhibited high tolerance and restoration capacity to heavy metals (HMs) stress. However, little is known about the mechanisms of HMs in S. officinale. In this study, transcriptomic and physiological changes of S. officinale response to different HMs (Pb, Cd and Zn) were analyzed and investigated the key genes and pathways involved in HMs uptake patterns. The results showed that phenotypic effects are not significant, and antioxidant enzyme activities were all upregulated. Transcriptome analysis indicated that 1247 differential genes were up-regulated, and 1963 differential genes were down-regulated under Cd stress, while 3752 differential genes were up-regulated, and 7197 differential genes were down-regulated under Pb stress; and 527 differential genes were up-regulated; and 722 differential genes were down-regulated under Zn stress. Based on their expression, we preliminarily speculate that different HMs resistance of S. officinale may be regulated by the differential expression of key genes. These results provide a theoretical basis for determining the exact expression of genes in plants under different heavy metal stress, the processes involved molecular pathways, and how they can be efficiently utilized to improve plant tolerance to toxic metals and improve phytoremediation efficiency.

The Biomechanical Screening Game between Visitor Power and Staminode Operative Strength of Delphinium caeruleum (Ranunculaceae).

During the evolution of angiosperm flowers, some floral traits may undergo certain changes in order to participate in screening. The stamens and pistils of Delphinium caeruleum are covered by two "door-like" staminodes, the evolutionary function of which, however, is quite unknown. In this study, we investigated whether D. caeruleum staminodes acted as visitor filters by assessing the respective strengths of staminodes and visitor insects (six bee species). We measured the operative strength required to open the staminodes and the strength that insects were capable of exerting using a biological tension sensor. Furthermore, we compared the strength required to open staminodes at different phases of the flowering period (male and female phases) and the strength of different visitors (visitors and non-visitors of D. caeruleum). The results showed that the strength needed to open staminodes in the male phase was significantly higher than that in the female phase. There was no significant difference between the strength exerted by visitors and required by staminodes of D. caeruleum in the male phase, but the visitor strength was significantly higher than that required to open staminodes in the female phase flowers. The strength of non-visitors was significantly lower than that required to open staminodes in the male phase. Furthermore, there was a significant positive association between the strength and the body weight of the bees. These results highlighted the observation that only strong visitors could press the two staminodes to access the sex organs and achieve successful pollination. Furthermore, these results revealed the function of pollinator screening by the staminodes of D. caeruleum. The biomechanical approach to the study of flowers allowed us to address relevant ecological and evolutionary questions of the plant-pollinator interaction and explore the functional modules within the flower structure in other plant species.