Auxin Response Factor Proteins
It has been discovered that specifically modifying auxin responses leads to improvements in biomass production and drought tolerance. The process can also be used to manipulate wood quality parameters.
Plant hormones, which act by inducing specific changes in gene expression, are the core regulators of almost every aspect of plant growth, development and environmental responsiveness. Hormones such as auxin, control a complex array of simultaneous processes. Cell, tissue and organ specific responses are determined at the level of transcriptional control.
Two families of transcriptional regulatory proteins have been discovered that are the primary means by which auxin is translated into specific responses. Both the Auxin Response Factor (ARF) and Aux/IAA families can positively or negatively regulate gene expression in response to auxin, depending on the cellular, developmental or environmental context.
By manipulating the levels of individual ARF proteins it is possible to modify specific auxin regulated processes. A T-DNA knockout mutant of one ARF family member resulted in plants with a dramatically increased capacity to withstand drought conditions.
Mutated plants survived lengthy periods where water was withheld, with little or no long-term impact once the plants had been rewatered. An alteration in the level of expression of another ARF family member led to a dramatic increase in above and below ground biomass production. This included a large increase in secondary xylem (wood) production.
Both of these genes appear to play roles in the determination of important wood quality parameters, such as lumen diameter, secondary cell wall thickness and vessel to fibre ratio.
The manipulation of the levels of these proteins in transgenic or conventionally bred plants may lead to increased drought tolerance, improved biomass production capacity and wood quality parameters that meet the needs of specific end uses in the modified plants.
- Dr Brian Jones
- Prof. Goran Sandberg
- Janet del Basani