AUREA maintains the balance between chlorophyll synthesis and adventitious root formation in tomato

Abstract

Flooding tolerance is an important trait for tomato breeding. In this study, we obtained a recessive mutant exhibiting highly enhanced submergence resistance. Phenotypical analyses showed that this resistant to flooding (rf) mutant displays slightly chlorotic leaves and spontaneous initiation of adventitious roots (ARs) on stems. The mutation was mapped to the phytochromobilin synthase gene AUREA (AU), in which a single amino acid substitution from asparagine to tyrosine occurred. In addition to the classic function of AU in phytochrome and chlorophyll biogenesis in leaves, we uncovered its novel role in mediating AR formation on stems. We further observed temporal coincidence of the two phenotypes in the rf mutant: chlorosis and spontaneous AR formation and revealed that AU functions by maintaining heme homeostasis. Interestingly, our grafting results suggest that heme might play roles in AR initiation via long-distance transport from leaves to stems. Our results present genetic evidence for the involvement of the AU–heme oxygenase-1–heme pathway in AR initiation in tomato. As fruit production and yield in the rf mutant are minimally impacted, the mutation identified in this study may provide a target for biotechnological renovation of tomato germplasm in future breeding.

A Mutation in CsHY2 Encoding a Phytochromobilin (PΦB) Synthase Leads to an Elongated Hypocotyl 1(elh1) Phenotype in Cucumber (Cucumis sativus L.)

“…For example, all reported mutants with mutations in the FBR domain, such as Arabidopsis hy2-1, hy2-104, hy2-101, and hy2-103 (Kohchi et al 2001), tomato au, au ls and au w (Terry and Kendrick. 1996;Muramoto et al 2005;Wu et al 2020), maize elm1, and rice se13 (Sawers et al 2002;Sawers et al 2004;Saito et al 2011;Reig-Valiente et al 2020), display common defective phenotypes with long hypocotyl and yellow green leaves as in the cucumber elh1 mutant identi ed herein that also carried an amino acid substitution (D104N) in the FBR domain (Figs. 1A-1D, 3D, S1; Supplemental le 3).…”

“…Therefore, this is not surprising that the role of CsHY2 in the synthesis of PΦB and Chl could explain the yellow green phenotype (Figs. 1C, 1D) in the elh1 plants, a phenotypic trait observed in most chromophore-de cient mutants (Weller et al 1997;Kraepiel et al 1994;Kohchi et al 2001;Sawers et al2002;Sawers et al 2004;Muramoto et al 2005;Zhu et al 2017;Wu et al 2020).…”

“…The FBR domain is crucial for catalytic performance, and mutations in the domain would lead to loss-of-function of HY2 and thus severely de cient in photoreversible phys (Terry and Kendrick. 1996;Kohchi et al 2001;Sawers et al 2002;Sawers et al 2004;Muramoto et al 2005;Wu et al 2020;Reig-Valiente et al 2020). For example, all reported mutants with mutations in the FBR domain, such as Arabidopsis hy2-1, hy2-104, hy2-101, and hy2-103 (Kohchi et al 2001), tomato au, au ls and au w (Terry and Kendrick.…”

“…Therefore, the disruption of PΦB synthesis could inactivate the entire phytochrome system and impairs photomorphogenesis (Sawers et al 2004). For example, all hy2 mutants in different plants, such as Arabidopsis hy2-1, tomato au, pea pcd2, tobacco pew2, and maize elm1 are characterized by an elongated hypocotyl and yellow-green phenotype due to a de ciency in photoactive phys (Weller et al 1997;Kraepiel et al 1994;Kohchi et al 2001;Sawers et al 2004;Muramoto et al 2005;Wu et al 2020).…”

A mutation in CsHY2 encoding a phytochromobilin (PΦB) synthase leads to an elongated hypocotyl 1(elh1) phenotype in cucumber (Cucumis sativus L.)

“…Therefore, the disruption of PΦB synthesis could inactivate the entire phytochrome system and impairs photomorphogenesis (Sawers et al 2004). For example, all hy2 mutants in different plants, such as Arabidopsis hy2-1, tomato au, pea pcd2, tobacco pew2, and maize elm1 are characterized by an elongated hypocotyl and yellow-green phenotype due to a de ciency in photoactive phys (Weller et al 1997;Kraepiel et al 1994;Kohchi et al 2001;Sawers et al 2004;Muramoto et al 2005;Wu et al 2020).…”