What is the molecular mechanism of odorant transduction signaling pathway?
Information available on this is huge. I will pin point main points. Generally this signalling will involve four components viz. receptors, transduction machinery, perireceptor processes and downstream processing of chemosensory information.

Receptors
First step is to receive signal (here odorant or chemicals). Following figure shows comparison between primary chemoreceptor neurons in vertebrates, insects, and nematodes.



These neurons constantly undergoes birth-maturation-death and process is well studied in many model systems. 

Signal transduction

After stimulus is received, it needs to be transfer inside cell for further processing. In this case, generally transduction happens via GPCR signalling. These neurons use two widely used signalling cascades. Following figure shows main components in this signalling ( (a):vertebrate olfactory receptor neurons (b): lobster olfactory receptor neurons),



Perireceptor Processes

These process are important for receptor activation and transduction. They can be any type like mechanical or biochemical.

Downstream processing

There is huge information available at the level of pathway. Following figure represents main components in two model systems.

 

For finding genes, you have to search in specific part of this process (like this is good example of receptor genes in human). 

I would strongly recommend reading chapter 4 of "The Senses - Comprehensive Reference". All above information is taken from this book. Another good open source reference is The Neurobiology of Olfaction, this reference has all things you need for free.