Draft:Mikhail E. Nasrallah

Mikhail Elia Nasrallah is Professor Emeritus in the Plant Biology Section of the School of Integrative Plant Science in the New York State College of Agriculture and Life Sciences  at Cornell University.

Education
Nasrallah, a native of Kfarmishki, Lebanon, received a Bachelor of Science degree in Agriculture and a certification in Agronomy [Ingénieur Agricole] from the American University of Beirut in 1960, a Master's degree in Horticulture from the University of Vermont in 1962, and a doctorate degree in Plant Breeding and Genetics from Cornell University in 1965.

Career and Research
Nasrallah carried out postdoctoral research at Cornell University from 1965-1967 and had a faculty position in Genetics at the State University of New York/Cortland from 1967 to 1985. He moved to Cornell University in 1985 and was appointed a Professor of Plant Biology in 1992.

Much of Nasrallah's research has focused on the molecular genetic analysis of self-incompatibility in plants of the crucifer (Brassicaceae) family. Self-incompatibility was first described as a genetic reproductive barrier that prevents a fertile plant having perfect flowers (i.e flowers containing both pistils and stamens) to produce zygotes and seed after self-pollination. This phenomenon, which is now known to prevent both self-pollination and mating among genetically-related plants, is the most prevalent mechanism used by angiosperms for preventing inbreeding and avoiding inbreeding depression, thus promoting outcrossing and ensuring the maintenance of genetic diversity in populations. This phenomenon has long puzzled and fascinated plant scientists, including Darwin who, based on his study of Fertilisation of Orchids, famously proclaimed it to be “… one of the most surprising facts which I have ever observed”.

Nasrallah is recognized as a pioneer in the study of self-incompatibility (SI). Over the course of his career, his work has resulted in numerous scientific publications which have been cited over 10,000 times (h-index=51). His research has also been featured in several perspective articles and paper alerts in high-impact journals, , , , , , , ,. As a doctoral student at Cornell, Nasrallah made a major scientific contribution by devising a new approach to the molecular analysis of SI. Instead of the pollen-centric focus which at the time had been the norm in research aimed at identifying the molecular components of SI in various plant families, he reasoned that investigating the contribution of the pistil to the SI response would be a more successful approach for identifying molecules involved in SI. Working in Brassica, he focused on the stigma, which is the structure that caps the pistil and at the surface of which “self” pollen grains are inhibited in self-incompatible crucifers. This approach led him to identify the first molecule encoded by an SI-determining gene. This strategy of using the pistil as a starting point for identifying the molecular components of SI has become common practice for molecular analysis of SI across various plant families.

The stigma molecule identified by Nasrallah was later used by his team at Cornell as a launching pad for a detailed analysis of the S locus, whose large number of variants (classically known as “alleles”) control recognition of “self” pollen in self-incompatible Brassica plants. This analysis led to the breakthrough demonstration that the S locus is a complex locus and that its “alleles” are in fact haplotypes each of which contains two genes that encode, respectively, the stigma and pollen determinants of SI: a receptor protein kinase displayed at the surface of the stigma epidermal cells that capture pollen and its small protein ligand located in the outer coating of pollen grains. Proof that these two genes are necessary and sufficient for determining specificity in the SI response was obtained by the Nasrallah team and others using gene transfer experiments,. Additionally, the two genes were found to be required for the outcrossing mode of mating in crucifers since they can restore SI when transferred into the normally self-fertile model plant Arabidopsis thaliana which lacks functional versions of these genes,.

The subsequent finding that the interaction of the stigma receptor with its pollen ligand, and hence receptor activation, is S haplotype-specific (i.e. they will only occur if the pollen ligand and the stigma receptor are derived from the same S haplotype) explained how the stigma can discriminate between self- and non-self pollen grains in self-incompatible crucifers,. This mechanism of self-recognition has now been shown to operate in all tested self-incompatible species from various genera, such as Brassica, Arabidopsis, and Capsella.

Awards and Honors
Nasrallah received the American University of Beirut's highest scholastic honor, the Penrose Award, in 1960 ; an award in Horticulture from the Burpee Foundation in 1961; and an award from the American Institute of Biological Sciences in 1970 in recognition of an outstanding research contribution related to a vegetable crop used for processing.