Diageotropica and lateral rooting, the rest of the story

Authors: Zobel, Richard

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2016
Publication Date: 8/5/2016
Citation: Zobel, R.W. 2016. Diageotropica and lateral rooting, the rest of the story. Frontiers in Plant Science. 7:1239.

Interpretive Summary: The developmental genetic control of lateral root initiation in dicotyledenous plants has been under study for over a century. A tomato mutant unable to develop lateral roots was discovered in the 1970’s, and, although described as an ethylene (a side product of plant growth and natural gas) requiring mutant by the original scientist, it was shortly latter classified as an auxin insensitive mutant. Thus no research on the mutant’s ethylene requiring nature has been done since. Recently the mutated gene was demonstrated to code for a compound that controls the localization of lateral roots on the parent root. This paper suggests that the levels of ethylene necessary to “normalize’ lateral rooting in the mutant are so low as to be catalytic rather than metabolic in action. It also concludes that there is a strong need to finally (40+ years later) determine the nature of this ethylene/mutant interaction. The result could revolutionize the understanding of plant hormonal interaction.

Technical Abstract: The nature of the control of lateral root initiation has been controversial for 80+ years. A mutant tomato (diageotropica), incapable of producing lateral roots, was first classified as ethylene requiring since exceptionally low concentrations of ethylene, applied to the shoot, stimulated lateral root initiation. Flawed early research with the mutant discounted the ethylene requiring nature and classified the mutant as auxin insensitive. The mutated gene has recently been demonstrated to normally code for a cyclophilin which is produced in the shoot and translocated to the roots where it controls the localization of auxin stimulated lateral root initiation. The mutant is a point mutation, thus a single amino acid is changed. The question is asked: how can ethylene at exceedingly low concentrations effect the normalization of the mutant cyclophilin and support its transport to the root system to direct lateral root initiation. The answer could have a major impact on auxin/ethylene crosstalk research.