Adrienne Clarke

University of Melbourne

Primary Section: 62, Plant, Soil, and Microbial Sciences
Secondary Section: 25, Plant Biology
Membership Type: International Member (elected 1993)

Research Interests

My work has been in two major areas. The first is the molecular biology of self-incompatibility, a mechanism whereby the pollen of a plant is recognized by the female sexual tissues of the same plant and rejected. In many systems the genetic control is through a single multi-allelic gene. We have discovered that in one system (gametophytic self-incompatibility in plants of the family Solanaceae), the gene controlling self-incompatibility in the female sexual tissues encodes an allelic series of ribonucleases. These ribonucleases are secreted into the extracellular matrix of the female transmitting tissue. As the pollen grows through the female transmitting tissue, it makes contact with the secreted ribonucleases and, in the case of selfpollen, the ribonuclease seems to be taken up into the pollen causing a slowing of the pollen tube growth. In that case pollen fails to reach the ovule and fertilization does not occur. The second field of research involves molecules of the extracellular matrix and cell walls. A family of glycoconjugates known as arabinogalactan-proteins (AGPs) is well represented in the extracellular matrix of most higher plants. The protein backbones of these glycoconjugates contain relatively high proportions of Pro/Hyp, Ser, Ala, and Thr. The carbohydrate is composed mainly of arabinose and galactose. I am particularly interested in the structure and function of these glycoconjugates. It seems that they are involved in such disparate functions as expression of cellular identity, control of differentiation, and gel matrix formation. We described the first gene encoding the protein backbones of several of these molecules and subsequently cloned a number of other genes encoding protein backbones of other members of this group, leading to grouping of the genes into several families. The structure/function relationships of these molecules is the next major research goal.

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