A protein unc-13 homolog, PATROL1 (PROTON ATPase TRANSLOCATION CONTROL 1), a protein with a MUN domain, is involved in the intercellular trafficking of the AHA1 H⁺-ATPase to the plasma membrane in guard cells of plants. This allows for larger stomatal opening and more efficient photosynthesis, leading to increased biomass. Although PATROL1 is expressed not only in stomata but also in other tissues of the shoot and root, the role in tissues other than stomata had not been determined. Notaguchi et al. 2024 investigated PATROL1 functions in roots using a loss-of-function mutant and an overexpressor. Cytological observations revealed that root meristematic size was significantly smaller in the mutant resulting in a short primary root. Grafting experiments showed that the shoot biomass of the mutant scion was increased when it grafted onto wild-type or overexpressor rootstocks. Conversely, grafting of the overexpressor scion shoot enhanced the growth of the mutant rootstock. The leaf temperatures of the grafted plants were consistent with those of their respective genotypes, indicating cell-autonomous behavior of stomatal movement and independent roles of PATROL1 in plant growth. Moreover, plasma membrane localization of AHA1 was not altered in root epidermal cells in the patrol1 mutant implying the existence of a different mode of PATROL1 action in roots. Thus, PATROL1 plays a role in root meristem and contributes to increased shoot biomass (Notaguchi et al. 2024).
References:
Hashimoto-Sugimoto, M., T. Higaki, T. Yaeno, A. Nagami, M. Irie, M. Fujimi, M. Miyamoto, K. Akita, J. Negi, K. Shirasu, S. Hasezawa, and K. Iba. (2013). A Munc13-like protein in Arabidopsis mediates H⁺-ATPase translocation that is essential for stomatal responses. Nat Commun 4: 2215.
Notaguchi, M., M. Ichita, T. Kawasoe, K. Monda, K.I. Kurotani, T. Higaki, K. Iba, and M. Hashimoto-Sugimoto. (2024). The PATROL1 function in roots contributes to the increase in shoot biomass. Planta 260: 105.
Examples:
TC#	Name	Organismal Type	Example
8.A.244.1.1	The Unc3 homolog, PATROL1, of 1101 aas. PATROL1 (PROTON ATPase TRANSLOCATION CONTROL 1), is a protein with a MUN domain. It is involved in the intercellular trafficking of AHA1 H⁺-ATPase (TC# 3.A.3.3.7) to the plasma membrane in guard cells (Notaguchi et al. 2024). This allows for larger stomatal opening and more efficient photosynthesis, leading to increased biomass. Thus, it controls the tethering of the proton ATPase AHA1 to the plasma membrane, and is essential for stomatal opening in response to low concentration of carbon dioxide and light (Hashimoto-Sugimoto et al. 2013).		*PATROL1 of Arabidopsis thaliana, (thale cress)*

8.A.244.1.2	Unc3 homolog, PATROL1, isoform X1, of 1107 aas. See family description for functionial activities.		PATROL1 of Triticum aestivum

8.A.244.1.3	PATROL1 homolog of 995 aas See family description for functional details.		PATROL1 of Populus alba x Populus berolinensis