Gmo Plants

The Plant Cell, Vol. 26: 585–601, February 2014, www.plantcell.org ã 2014 American Society of Plant Biologists. All rights reserved.

Tomato GOLDEN2-LIKE Transcription Factors Reveal

Molecular Gradients That Function during Fruit

Development and Ripening

W OPEN

Cuong V. Nguyen,a,b Julia T. Vrebalov,b Nigel E. Gapper,b Yi Zheng,b Silin Zhong,b,c Zhangjun Fei,b,d

and James J. Giovannonib,d,1

a Department

of Plant Breeding and Genetics, Cornell University, Ithaca, New York 14853

Thompson Institute for Plant Research, Ithaca, New York 14853

c School of Life Sciences, Chinese University of Hong Kong, Sha Tin, Hong Kong

d U.S. Department of Agriculture/Agriculture Research Service, Robert W. Holley Centre for Agriculture and Health, Ithaca, New York

14853

b Boyce

Fruit ripening is the summation of changes rendering fleshy fruit tissues attractive and palatable to seed dispersing

organisms. For example, sugar content is influenced by plastid numbers and photosynthetic activity in unripe fruit and later by

starch and sugar catabolism during ripening. Tomato fruit are sinks of photosynthate, yet unripe green fruit contribute

significantly to the sugars that ultimately accumulate in the ripe fruit. Plastid numbers and chlorophyll content are influenced

by numerous environmental and genetic factors and are positively correlated with photosynthesis and photosynthate

accumulation. GOLDEN2-LIKE (GLK) transcription factors regulate plastid and chlorophyll levels. Tomato (Solanum

lycopersicum), like most plants, contains two GLKs (i.e., GLK1 and GLK2/UNIFORM). Mutant and transgene analysis

demonstrated that these genes encode functionally similar peptides, though differential expression renders GLK1 more

important in leaves, while GLK2 is predominant in fruit. A latitudinal gradient of GLK2 expression influences the typical uneven

coloration of green and ripe wild-type fruit. Transcriptome profiling revealed a broader fruit gene expression gradient...