biologia plantarum

Biologia plantarum 62:353-361, 2018 | DOI: 10.1007/s10535-017-0762-3

The tomato cytosolic fructokinase FRK1 is important for phloem fiber development

O. Stein^1,2, F. Secchi³, M. A. German¹, H. Damari-Weissler¹, R. Aloni⁴, N. M. Holbrook⁵, M. A. Zwieniecky⁶, D. Granot^1,*

¹ Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel

² The Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel

³ Department of Agricultural, Forest and Food Sciences, University of Torino, Grugliasco, TO, Italy

⁴ Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv, Israel

⁵ Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, USA

⁶ Department of Plant Sciences, University of California, Davis, USA

Tomato (Solanum lycopersicum) plants have four fructokinase genes, SlFRK1-4. The SlFRK4 is expressed only in pollen whereas the other three are expressed in all plant parts. While SlFRK2 and SlFRK3 are involved in vascular tissue development and affects the shape, size, and cell-wall width of xylem vessels and xylem fibers, the role of SlFRK1 has not been studied previously. The current work investigates the expression of SlFRK1 using transgenic tomato plants expressing the β-glucuronidase reporter gene under the SlFRK1 promoter, as well as the role of SlFRK1 using transgenic plants with antisense suppression of SlFRK1. The SlFRK1 promoter is expressed primarily in vascular tissues and specific suppression of SlFRK1 reduces water transport in stems, but has no other anatomical or phenotypic effects. Combined suppression of SlFRK1 and SlFRK2 severely inhibited plant growth and an anatomical analysis revealed a reduction in secondary xylem area and distorted phloem fibers characterized by thin cell walls and reduced lignification. The results suggest that SlFRK1 is involved in vascular tissue development and hydraulic conductivity in tomato plants and that SlFRK1 is important for normal phloem fiber development, together with SlFRK2.

Keywords: cell walls; hydraulic conductivity; lignification; water transport; xylem vessels

Subjects: fructokinase; phloem fiber development; cell wall; lignification; hydraulic conductivity; FRK genes; xylem anatomy; tomato

Received: February 17, 2017; Revised: May 18, 2017; Accepted: June 12, 2017; Published: June 1, 2018  Show citation