The involvement of ER-sHsp21.5 in the tomato development and postharvest chilling tolerance

MARIELA R. ESCOBAR; SILVANA B. BOGGIO; MA. LAURA SOSSI; MA. INES ZANOR; DIEGO J. RENZI; ESTELA M. VALLE

Congreso; XXXIII Argentinian meeting of Plant Physiology; 2021

Tomato (Solanum lycopersicum) fruit is a valuable horticultural crop worldwide. Usually, non-freezing low-temperature storage is applied after harvesting. However, the production yield and the fruit quality can be severely impaired by chilling injury. A previous study showed transcriptional up-regulation of genes coding for small heat shock proteins (sHsps) associated with postharvest chilling tolerance. sHsps are proposed to act as molecular chaperones to protect other proteins from stress-induced damage and in plants are remarkably diverse and numerous. This diversity comprises classes including proteins targeted to the cytosol, nucleus, endoplasmic reticulum, chloroplast, mitochondria, and peroxisome. To explore the role of endoplasmic reticulum-located small heat-shock proteins 21.5 (ER-sHsp21.5), we constructed Micro-Tom transgenic plants overexpressing and silencing the ER-sHsp21.5 gene under the control of the fruit specific phosphoenolpyruvate carboxylase isoform gene (PPC2) promoter. The phenotypic characteristics of the silenced and overexpressing plants, seeds, and flowers indicate that ER-sHsp21.5 participates in the plant development processes. Both the overexpressing and the silenced fruits were more susceptible to postharvest chilling than the wild-type fruits, showing that the ER-sHsp21.5 concentration should be optimal to develop postharvest chilling tolerance. Also, the color and pigment content analyses showed that ER-sHsp21.5 has a possible role in regulating the β-carotene and lycopene synthesis and protecting the post-chilling color development process. These results show that the ER-sHsp21.5 roles in the plant are diverse and complex.