Biological complexity: how plants wither old parts (Introduction)

by David Turell , Thursday, April 14, 2016, 15:25 (2927 days ago) @ David Turell

It is a very complex molecular mechanism with a giant molecule at the center of the reactions:-https://www.sciencedaily.com/releases/2016/04/160414081845.htm-"During their life, plants constantly renew themselves. They sprout new leaves in the spring and shed them in the fall. No longer needed, damaged or dead organs such as blossoms and leaves are also cast off by a process known as abscission-***-"It was already known that the membrane receptor protein HAESA and a small peptide -a short chain of amino acids -- hormone called IDA are involved in the same signaling pathway and, together, control the shedding of floral organs. So far, however, the mechanism underlying their interaction was poorly understood," explaind Michael Hothorn, professor at the Department of Botany and Plant Biology of the Faculty of Science of UNIGE. By solving the crystal structure of HAESA (from the Greek 'to shed') in complex with IDA, Hothorn and his team found out that the receptor directly senses the peptide hormone. They observed that HAESA contains a small cleft into which IDA fits perfectly. However, it only binds halfway to the receptor. To fully initiate the abscission process, another player is needed: the helper protein SERK1. IDA then works like a double-sided Scotch tape that tethers the entire complex together. The binding of SERK1 to HAESA and IDA triggers the molecular switch that instructs the cell to shed the organ.-"'The fascinating thing about SERK1 is that it not only plays a role in the shedding mechanism of plant organs, but also acts together with other membrane receptors that regulate totally different aspects of plant development," says Julia Santiago, first author of the study. Indeed, SERK1 is a versatile helper protein shared between different signaling pathways. When bound to another protein receptor, it can also for example signal the plant to grow."-Comment: The process is partially understood. Look at the model. ISA is not a 'short' chain', just smaller than its two giant partners. These are giant specialized molecules. How did Darwin-style evolution find them from the available supply of possibilities? The lock and key model is a standard pattern in the biochemistry of life.