Activation-tagged tobacco mutants that are tolerant to antimicrotubular herbicides are cross-resistant to chilling stress

Abstract

T-DNA activation tagging was used to generate tobacco mutants
with increased tolerance to antimicrotubular herbicides and
chilling stress. After transformation, protoplast-derived calli
were screened for tolerance to treatments that affect
microtubule assembly. In one screen mutants with tolerance to
aryl carbamates (a blocker of microtubule assembly) were
selected, the second screen was targeted to chilling-tolerant
mutants that could survive for several months at 3°C, a third
screen combined both factors. The resistance of these mutants to
aryl carbamates or chilling was accompanied by resistance of
microtubules to these factors. The carbamate tolerant mutants
were crossresistant to chilling stress. This was mirrored by an
adaptive reorganization of microtubules and a reduction of
microtubule dynamics in response to chilling. The analysis of
these mutants suggests (1) that microtubule dynamics limit the
tolerance to chilling and EPC, and (2) that the cold sensitivity
of microtubules limits chilling tolerance in tobacco.

Key words: activation tagging, antimicrotubular herbicides, aryl
carbamates, chilling tolerance, microtubules, tyrosinylated tubulin