Molecular Cloning and Expression Analysis of a Putative 5′-3′ EXORIBONUCLEASE4 (XRN4) Gene from Tomato

Abstract

Arabidopsis thaliana 5′-3′ EXORIBONUCLEASE4 (AtXRN4) is involved in the degradation of multiple unstable mRNAs and plays important roles in ethylene response, disease resistance and miRNA-mediated RNA decay. However, XRN4-like genes are completely unknown in tomato—an important model system for studying the biological basis of fleshy fruit development. The present study reports on the identification of a putative 5′-3′ EXORIBONUCLEASE gene from tomato. The encoded protein was designated SlXRN4 due to its greater similarity to AtXRN4 and the cytoplasm-localizing trait. SlXRN4 is expressed in major reproductive and vegetative tissues, and is regulated by ethylene and auxin treatment. In floral buds and flowers, SlXRN4 displays distinct strongest expression in stamens. Transcripts of SlXRN4 increase slightly in ovary, petal, and sepal, but accumulate dramatically in stamen during bud-to-anthesis transition, and decline in ovary and sepal during anthesis-to-post-anthesis when fruit set is expected to occur. SlXRN4 expression decreases gradually from ovary to mature green during fruit development, and increases rapidly at the breaker stage when fruit ripening is beginning. The dynamic expression of SlXRN4 suggests a role in regulating critical stages of flower and fruit development in tomato, which provides helpful clues for further study of the physiological function of 5′-3′ EXORIBONUCLEASE4 in tomato.