A Plant Small Heat Shock Protein Gene Expressed during Zygotic Embryogenesis but Noninducible by Heat Stress

Raúl Carranco,Concepción Almoguera,Juan Jordano

doi:10.1074/jbc.272.43.27470

Raúl Carranco, Concepción Almoguera + Show 1 more

Open Access

https://doi.org/10.1074/jbc.272.43.27470

Copy DOI

Abstract

A small heat shock protein (sHSP) gene from sunflower, Ha hsp17.6 G1, showed expression patterns that differ from what is known for members of this gene family. The mRNAs of this gene accumulated in seeds during late desiccation stages of zygotic embryogenesis but not in response to heat shock in vegetative tissues. The failure to respond to heat shock was independent of the developmental stage after germination and shock temperature. Nuclear run-on analyses demonstrated that transcription from the Ha hsp17.6 G1 promoter is not induced by heat shock. This agrees with the presence, in this promoter, of sequences with little similarity to heat shock elements. Our results show an evolutionary divergence, in the regulation of plant sHSP genes, which has originated stress-responsive genes and nonresponsive members within this gene family. We discuss implications for mechanisms controlling the developmental regulation of sHSP genes in plants.

Highlights

In addition to being part of the heat shock response, some plant small heat shock protein (sHSP) genes have been shown to be expressed at normal growth temperatures during zygotic embryogenesis (4 –7)
There is no obvious explanation for the differential regulation of a subset of sHSP genes during embryogenesis, and such regulation might involve control elements that are common and/or distinct from those involved in the heat shock response
We describe and analyze the genomic sequences of Ha hsp17.6 G1, a sunflower sHSP gene expressed during zygotic embryogenesis [6]

Summary

Introduction

In addition to being part of the heat shock response, some plant sHSP genes have been shown to be expressed at normal growth temperatures during zygotic embryogenesis (4 –7). By detailed analyses of gene-specific mRNA accumulation and transcription, we demonstrate that transcription from the Ha hsp17.6 G1 promoter is not induced in response to heat shock.

Results

Conclusion