Loss-of-function of MEDIATOR 12 or 13 subunits causes the swelling of root hairs in response to sucrose and abscisic acid in Arabidopsis

ABSTRACT

Root hairs are epidermal cell extensions that increase the root surface for water and nutrient acquisition. Thus, both the initiation and elongation of root hairs are critical for soil exploration and plant adaptation to ever changing growth conditions. Here, we describe the critical roles of two subunits of the Mediator complex, MED12 and MED13, in root hair growth in response to sucrose and abscisic acid, which are tightly linked to abiotic stress resistance. When compared to the WT, med12 and med13 mutants showed increased sensitivity to sucrose and ABA treatments on root meristem and elongation zones that were accompanied with alterations in root hair length and morphology, leading to the isodiametric growth of these structures. The swollen root hair phenotype appeared to be specific, since med8 or med16 mutants did not develop rounded hairs when supplied with 4.8% sucrose. Under standard growth medium, MED12 and MED13 were mainly expressed in root vascular tissues and cotyledons, and their expression was repressed by sucrose or ABA. Interestingly, med12 and med13 mutants manifested exacerbated levels of nitric oxide under normal growth conditions, and upon sucrose supplementation in trichoblast cells, which coincided with root hair deformation. Our results indicate that MED12 and MED13 play non-redundant functions for maintenance of root hair integrity in response to sucrose and ABA and involve nitric oxide as a cellular messenger in Arabidopsis thaliana.

KEYWORDS:

• Arabidopsis thaliana
• root hair development
• abscisic acid
• sucrose
• mediator complex

Acknowledgments

The authors thank Dr Stewart Gillmor for kindly providing Arabidopsis transgenic seeds.

Disclosure statement

No potential conflict of interest was reported by the authors.

Author contribution statement

JCPR and LFRH conducted experiments. JLB and LFRH conceived and designed research. JLB and JRG analyzed the data. JLB and JRG wrote the manuscript. All authors read and approved the manuscript.

Data availability statement

The datasets generated during the current study are available from corresponding authors upon reasonable request.

Additional information

Funding

This work was founded by grants from Secretaría de Educación Pública (SEP)-Consejo Nacional de Ciencia y Tecnología (CONACYT) A1-S-34758.