New National Excellence Program-result summary

Dear Readers!

A long time has elapsed since the last post. A lot had happened in the meantime, but now, I would like to present a summary of my results in the topic of ROP-NO interactions.

My experiments were supported by the New Excellence Program of the Ministry of Human Capacities.

The summary of my main observations:

Nitric oxide (NO) is a gaseous signal molecule which in cooperation with auxin regulates root developmental processes like primary root or root hair elongation and lateral root formation. Some of these physiological processes take place with the participation of plant-specific regulator Rho of Plants (ROP) proteins which are known to interact with auxin. ROPs act as molecular switches due to conformational changes upon GTP binding and hydrolysis facilitating transient interactions with effector proteins. Although, NO and ROPs as regulators share common interacting partner (auxin) and physiological process (root growth), their crosstalk has not been proven so far. My study aims therefore to examine a suspected ROPs-NO signal interplay in plants. I developed an experimental system, in which the NO sensing of different ROP mutant and reporter Arabidopsis lines were evaluated.

     Compared to the wild-type (Col-0), rop2-1 and rop2-2 roots showed significant NO insensitivity, while rop6 responded to the presence of NO donors similarly to Col-0 (NO-induced root meristem shortening). In agreement with this, neither the rate nor the pattern of ROP6 in situ expression was affected by NO supplementation. The in situ expression of ROP2; however, decreased in the presence of NO, as well as the PIN-dependent auxin transport and auxin maximum in the root tip. Moreover, both rop2 mutants possess elevated endogenous NO level in their root tip compared to Col-0, which further support the connection between NO and ROP2 signalling the root meristem.

     Based on the results we can strongly suspect that exogenous NO negatively influences ROP2 action thus inhibits polar auxin transport and consequently the generation of auxin maximum leading to root meristem shortening. To confirm this conclusion, my further experiments will focus on providing direct evidence for the involvement of ROP2 in NO-induced root meristem shortening.

The effect of S-nitrosoglutathione (250 uM GSNO, NO donor) on PIN1::GFP expression in Arabidopsis primary root tips. Bars= 50 µm. n=10±SE, **P≤0.01, Student t-test.

Acknowledgements: this work was Supported by the unkp-17- 4 new national excellence program of the ministry of human capacities.