A petition signed by 114 professors from four countries calls for a UC Berkeley faculty investigation and a public accounting by the chancellor for denying tenure to an assistant professor, the professor's supporters said Tuesday.

Ignacio Chapela, who has taught microbial ecology at Cal, believes his tenure denial is linked to his criticism of the university's ties to the biotech industry. His contract expires June 30, according to campus officials.

The petition, also endorsed by the Cal graduate student assembly, calls on the faculty senate to investigate Chapela's tenure review and asks Chancellor Robert Berdahl to explain why he "went against the recommendations of nearly 60 people involved in the tenure process."

Cal spokesman George Strait said campus officials cannot comment on personnel matters, but he described the eight-step tenure process "as among the most rigorous in the country."

Chapela and a graduate student published a disputed study in Nature saying genetically engineered corn had infiltrated native maize in Mexico. Nature later issued a de facto retraction, saying "that the evidence available is not sufficient to justify the publication of the original paper."