What IB424 is about
Developmental biology focuses on the mechanisms by which the integrated, higher level of organization characteristic of all multicellular life forms comes about. This focus is therefore fundamentally different from issues within the perhaps more familiar biochemical and molecular disciplinary foundations upon which development rests. Those accustomed to thinking about these lower levels of biological organization and inquiry can take comfort in the assurance that developmental phenomena do in fact ultimately come down to molecules and their interactions. Nothing metaphysical here. Yet development entails a global-local interplay among cells, tissues and organs that resembles in some ways the complexity of ecosystem and community ecologies. Importantly, however, development displays a striking robustness in the face of exogenous challenges and endogenous genetic variation, driven of course by the ultimate obligation of every organism: to progress to successful reproductive maturity.
Multicellularity is the fundamental design feature common to all 'higher' life forms. Plants and animals are thus emergent phenomena ultimately reducible to diverse mitotic lineages of very smart cells, each sumptuously endowed from birth with the entire instruction set (the genome) that has evolved to both build and operate reproductively successful individuals of the current version of the species of which that cell is to become but a tiny part. From first principles, one might assume that knowing all the instructions carried by these omniscient (from the standpoint of the organism) building blocks would suffice for understanding how their cooperative body-building enterprise is orchestrated. But that assumption stumbles as we recognize that the fates of cells in a developing organism, especially in a plant, are guided not only by internal instructions from the identical genome that each inherits, but also potently by that genome's responses to the stream of physical and chemical signals each receives from its neighbors and from the ambient environment, be it maternal tissue or the outside world, as development proceeds. The need for special tools to gather and analyze data that encompass such dynamics and complexity has long been recognized and some powerful research tools are now emerging and being implemented in increasingly sophisticated fashions in the service of constructing authentic models of developing systems.
In IB424, we explore the mechanisms guiding the construction of higher plants, beginning with the single-celled zygote that forms when pollen successfully fertilizes the egg nucleus in an ovule of a flower. We begin with a few sessions considering essential conceptual issues such as those alluded to above. We then work our way through the plant, from embryogeny to roots, leaves and flowers. Most of the data we discuss come from the genetics of Arabidopsis thaliana, the model dicot that has yielded fantastic insights in plant developmental genetics in recent decades. As time permits, cases are included from other important model systems such as maize, rice, snapdragon and tomato.
Our approach is decidedly conceptual rather than aimed at compiling catalogues of diverse genes, phenomena and trivia. This preference arises from the recognition that plant genomes encode upwards of 25,000 genes, the majority of which probably play key roles in developmental events. Therefore, there are just too many genes to learn and remember. Mercifully (and of fascinating evolutionary import), the emerging picture of plant developmental genetics depicts an accessibly finite set of themes involving, among others, key biophysical principles and genetic motifs of transcriptional and post-transcriptional control and metabolic signaling. Thus, our focus is on identifying recurring, core mechanisms and principles, via examples drawn from specific, familiar developmental pathways in plants. In so doing, my hope is to give the course "legs", to provide a framework onto which you can map new data encountered after the conclusion of your experience in IB424.
This is always a relatively small class and therefore discussion and questions are strongly encouraged. Readings are assigned from a recommended textbook(s) and from short review articles accessed from the course website. Periodically we turn the class into a Journal Club. The purpose of the Journal Club is threefold: (1) to familiarize you with current questions and techniques in plant developmental research, (2) to reduce or eliminate your intimidation with respect to the literature reporting current research, and, (3) to prepare you for writing a research proposal at the end of the semester in IB424. Grades in IB424 are assigned based on three exams, journal club exercises and a term paper. This paper is weighted more towards research proposal format for graduate students than it is for undergrads.
If you have any questions about the course, please feel free to email me.