A Family of at Least Seven β-Galactosidase Genes Is Expressed during Tomato Fruit Development

Abstract

During our search for a cDNA encoding ␤-galactosidase II, a ␤-galactosidase/exogalactanase (EC 3.2.1.23) present during tomato (Lycopersicon esculentum Mill.) fruit ripening, a family of seven tomato ␤-galactosidase (TBG) cDNAs was identified. The shared amino acid sequence identity among the seven TBG clones ranged from 33% to 79%. All contained the putative active site-containing consensus sequence pattern G-G-P-[LIVM]-x-Q-x-E-N-E- [FY] belonging to glycosyl hydrolase family 35. Six of the seven single-copy genes were mapped using restriction fragment length polymorphisms of recombinant inbred lines. RNA gel-blot analysis was used to evaluate TBG mRNA levels throughout fruit development, in different fruit tissues, and in various plant tissues. RNA gel-blot analysis was also used to reveal TBG mRNA levels in fruit of the rin, nor, and Nr tomato mutants. The TBG4-encoded protein, known to correspond to ␤-galactosidase II, was expressed in yeast and exo-galactanase activity was confirmed via a quantified release of galactosyl residues from cell wall fractions containing ␤(134)-d-galactan purified from tomato fruit.

Alleviation of postharvest chilling injury of tomato fruit by salicylic acid treatment

“…Mature green fruit (40-42 DPA) at the MG4 stage were used for salicylic acid treatment. The MG4 stage was confirmed by cutting fruit open and observing entirely liquefied locular gel and no cut seeds (Smith and Gross 2000). About 500 fruit were manually picked and immediately transferred to the laboratory.…”

Biochemistry of fruit softening: an overview

“…Seven tomato β-galactosidase (TBG) genes are expressed during fruit development (Smith and Gross, 2000), six are known to be expressed during ripening. β-Galactosidase proteins have also been purified and characterized from a number of fruits including kiwifruit (Ross et al, 1993), coffee (Golden et al, 1993), persimmon (Kang et al, 1994), and apple (Ross et al, 1994).…”

Differentially expressed genes in healthy and plum pox virus-infected Nicotiana benthamiana plants

“…β-galactosidase can release stored energy for rapid growth (xyloglucan mobilization in cotyledons), act at metabolic recycling of galactolipids and glycoproteins, or degrade cell wall components during senescence. It has been shown important for fruit ripening (Smith and Gross, 2000). However, scarce data are available about possible role of β-galactosidase in plant-pathogen interactions.…”