Clay Carter

Our group has several broad research interests, including plant-microbe and plant-animal interactions, as well as protein trafficking in plant cells. Each of these broad interests are currently being pursued through several integrated projects revolving around nectaries and nectar.

Flowering plants attract mutualistic animals by offering a reward of nectar. Specifically, floral nectar is produced to attract pollinators, whereas extrafloral nectar mediates indirect defenses (e.g. ant-plant interactions). There is a strong correlation between nectar quality (i.e. volume and composition) and the efficiency of the resulting plant-animal mutualism. Significantly, there is also a clear relationship between nectary form (the glands that produce nectar) and nectar quality. Remarkably, the molecular events involved in the development of nectaries, as well as the synthesis and secretion of the nectar itself, are poorly understood. Indeed, only a few genes have been reported to directly affect the de novo production or quality of floral nectar.

Comparative genomics of nectaries and nectar

According to our recent findings, the central components of active nectar secretion might be conserved across species and nectary type (floral vs. extrafloral). We hypothesize that nectar synthesis and secretion follows a central mechanism that is conserved among the core eudicots and applies to both floral and extrafloral nectar, and that this mechanism can be differentially regulated in different types of tissues, or species, in order to meet the physiological and ecological needs of the respective species. To test this hypothesis,the long-term goal of our group is to elucidate the genetic and physiological mechanisms that underlie nectary maturation and active nectar secretion, and to study the impact of select nectar components on specific plant-animal and plant-microbe interactions. In order to elucidate the conserved elements of these mechanisms we are applying a broad, comparative approach to the study of floral and extrafloral nectar/ies in a core group of dicotyledonous species.

Determining the molecular basis of nectar production can have broad implications, ranging from understanding the co-evolution of plant-animal interactions to increasing yields in multiple crop species, as well as targeted improvements in apiculture. For example, nearly 90% of flowering plant species produce nectar as a means to attract pollinators, including one-third of all crop species. U.S. pollinator-dependent crops have an estimated annual value of $25 billion.

Development of cultivars with increased nectar production

In a separate project we are developing crop plants with high levels of floral nectar production. An increase in nectar production results in a concomitant increase in pollinator visitation, pollination efficiency, and yield, even for highly selfing plant species. For example, pennycress is an emerging winter cover and seed crop and is one of the first cultivated plants to flower in Minnesota (mid-April to early May). Our hypothesis is that cultivated pennycress may serve as an important source of nutrition for honeybees and other pollinators in the spring when other plants are not yet flowering at an appreciable level in Minnesota. In particular, the development pennycress plants with enhanced nectar production would provide an important ecosystem service. Pollinator nutrition has become an area of intense research as a means to stem declining pollinator numbers, particularly for honey bees. Cultivars with stably enhanced levels of nectar production are now being developed and will be evaluated for their ability to impact pollinator visitation and yield.