2. 4. 2019
PIN auxin transporters in evolution of root gravitropism and flowering during conquest of land by plants
prof. Jiri Friml, Ph.D., Dr.rer.nat.
(Institute of Science and Technology Austria (IST Austria))
The ultimate conquest of the dry land by plants started in the Late Devonian when the early diverging seed plants underwent dramatic evolutionary radiations and became the dominant group in the dry environment. Key adaptions were the efficient root gravitropism (enabling to reach water and nutrients) and flowering (allowing for moisture-independent fertilization). Here, we provide first insights into evolution of both processes, mainly from the point of view of the PIN-dependent auxin transport.
Architectural innovation with root tip-localized gravity perception appeared only at the onset of the seed plant advancement. Two-step functional innovation within the family of PIN auxin transporters led to evolution of gravitropism-specific PIN2 with its unique apical, subcellular localization, which was the major evolutionary invention that enabled connecting the anatomically separated place of gravity perception and growth response by the mobile auxin signal.
For evolution of flowering, we revealed a three-step evolutionary innovation within PIN gene family ultimately leading to evolution of Angiosperms-specific PIN1. They involve roles in: (i) shoot and root development at the onset of land plant advancement; (ii) inflorescence development at the origin of vascular plants; and (iii) floral organ formation in flowering plants.
Because of these evolutionary innovations seed plants were able to overcome the past environmental restrictions and successfully colonize the dry land where their predecessor failed to arrive.