MYB transcription factors (TFs) are involved in diverse biological,
functional, and structural processes. Previously, very few studies on R2R3
MYB have been conducted in cotton in response to abiotic stresses. Hamama
Islam Butt from the Institute of Cotton Research of Chinese Academy of
Agricultural Science expressed GaMYB85, a cotton R2R3 MYB TF, in Arabidopsis
thaliana to study the function of the TF in the transgenic plants.
Arabidopsis plants overexpressing GaMYB85 exhibited a higher seed
germination rate in response to mannitol and salt stresses, and higher
drought avoidance efficiency than wild-type plants. These plants also had
notably higher levels of free proline and chlorophyll with subsequent lower
water loss rates and higher relative water content.
Germination of GaMYB85 transgenics was found to be more sensitive to
abscisic acid (ABA). Moreover, when subjected to treatment with different
concentrations of ABA, transgenic plants showed reduced stomatal density,
with greater stomatal size and lower stomatal opening rates than wild-type
plants. Expression of GaMYB85 led to enhanced expression of stress-related
marker genes such as RD22, ADH1, RD29A, P5CS, and ABI5.
These results show previously unknown roles of GaMYB85. This study found
that it confers good drought, salt, and freezing tolerance, via an
ABA-induced pathway. This TF can potentially be used to develop improved
abiotic stress tolerance in cotton.