Circadian clocks of both plants and pollinators influence flower seeking behavior of the pollinator hawkmoth Manduca sexta.

Most plant-pollinator interactions occur during specific periods during the day. To facilitate these interactions, many flowers are known to display their attractive qualities, such as scent emission and petal opening, in a daily rhythmic fashion. However, less is known about how the internal timing mechanisms (the circadian clocks) of plants and animals influence their daily interactions. We examine the role of the circadian clock in modulating the interaction between Petunia and one of its pollinators, the hawkmoth Manduca sexta. We find that desynchronization of the Petunia circadian clock affects moth visitation preference for Petunia flowers. Similarly, moths with circadian time aligned to plants show stronger flower-foraging activities than moths that lack this alignment. Moth locomotor activity is circadian clock-regulated, although it is also strongly repressed by light. Moths show a time-dependent burst increase in flight activity during subjective night. In addition, moth antennal responsiveness to the floral scent compounds exhibits a 24-hour rhythm in both continuous light and dark conditions. This study highlights the importance of the circadian clocks in both plants and animals as a crucial factor in initiating specialized plant-pollinator relationships.

Constitutive expression of the maize genes B1 and C1 in transgenic Hi II maize results in differential tissue pigmentation and generates resistance to Helicoverpa zea.

Anthocyanin biosynthesis in maize protects tissues from biotic and abiotic stresses. Constitutive expression of the maize B1 and C1 genes, which induces anthocyanin biosynthesis, resulted in transgenic plants with varied phenotypes. Some colored leaves were substantially resistant to thrips damage, while only leaves with the highest levels of cyanidin, the predominant anthocyanidin detected in all colored transgenic tissues, were resistant to corn earworm (CEW) larvae. Colored anthers were resistant to CEW feeding, and reductions in CEW growth were significantly correlated to levels of cyanidin in the anthers. Cyanidin chloride and cyanidin-3-glucoside chloride added to insect diet slowed the growth of CEW larvae. Attempts to produce 3'5'-hydroxylated anthocyanins in colored maize with the expression of a petunia F3'5'H hydroxylase gene were unsuccessful.