The same anthocyanins served four different ways: Insights into anthocyanin structure-function relationships from the wintergreen orchid, Tipularia discolor

Over 500 unique anthocyanins have been described to date, which vary in color, antioxidant, light-attenuating, and antimicrobial properties. Identification of anthocyanin chemical structure may therefore serve as an important clue to their in situ function in plants. We characterized the histological and chemical structures of anthocyanins associated with diverse leaf color patterns in the terrestrial orchid, Tipularia discolor, as a step towards understanding their ultimate function. Tipularia discolor produces a single wintergreen leaf in autumn, which is drab brown in color during expansion. Upper (adaxial) surfaces of fully-expanded leaves may be green, purple-spotted, or solid purple, while lower (abaxial) surfaces are bright magenta. Our results showed that the same three cyanidin 3,7,3'-triglucosides, in similar concentrations and proportions, accounted for coloration in each of these cases, and that different colors result from differences in histological location of anthocyanins (i.e. abaxial/adaxial epidermis, mesophyll). Anthocyanins with 3,7,3' linkage positions are rare in plants, occurring only within the orchid subfamily Epidendroideae, to which Tipularia belongs. These results are important to the discussion of anthocyanin structure-function because they serve as a reminder that 1) plants may employ the same anthocyanins in different anatomical locations to achieve a broad range of colors (and potentially adaptive functions), and 2) anthocyanin chemical structure and anatomical location are influenced by phylogenetic inertia, as well as natural selection.

Piriformospora indica colonization increases the growth, development, and herbivory resistance of sweet potato (Ipomoea batatas L.)

Piriformospora indica symbiosis promoted the growth and photosynthesis, and simultaneously enhanced the resistance against insect herbivory by regulating sporamin-dependent defense in sweet potato. Piriformospora indica (P. indica), a versatile endophytic fungus, promotes the growth and confers resistance against multiple stresses by root colonization in plant hosts. In this study, the effects of P. indica colonization on the growth, physiological change, and herbivore resistance of leaf-vegetable sweet potato cultivar were investigated. P. indica symbiosis significantly improved the biomass in both above- and under-ground parts of sweet potato plants. In comparison with the non-colonized plants, the content of photosynthetic pigments and the efficiency of photosynthesis were increased in P. indica-colonized sweet potato plants. Further investigation showed that the activity of catalase was enhanced in both leaves and roots of sweet potato plants after colonization, but ascorbate peroxidase, peroxidase, and superoxide dismutase were not enhanced. Furthermore, the interaction between P. indica and sweet potato plants also showed the biological function in jasmonic acid (JA)-mediated defense. The plants colonized by P. indica had greatly increased JA accumulation and defense gene expressions, including IbNAC1, IbbHLH3, IbpreproHypSys, and sporamin, leading to elevated trypsin inhibitory activity, which was consistent with a reduced Spodoptera litura performance when larvae fed on the leaves of P. indica-colonized sweet potato plants. The root symbiosis of P. indica is helpful for the plant promoting growth and development and has a strong function as resistance inducers against herbivore attack in sweet potato cultivation by regulating sporamin-dependent defense.