Caspase-like activities accompany programmed cell death events in developing barley grains.

Van Tran,Diana Weier,Johannes Thiel,Ruslana Radchuk,Volodymyr Radchuk

doi:10.1371/journal.pone.0109426

Van Tran, Diana Weier + Show 3 more

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https://doi.org/10.1371/journal.pone.0109426

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Abstract

Programmed cell death is essential part of development and cell homeostasis of any multicellular organism. We have analyzed programmed cell death in developing barley caryopsis at histological, biochemical and molecular level. Caspase-1, -3, -4, -6 and -8-like activities increased with aging of pericarp coinciding with abundance of TUNEL positive nuclei and expression of HvVPE4 and HvPhS2 genes in the tissue. TUNEL-positive nuclei were also detected in nucellus and nucellar projection as well as in embryo surrounding region during early caryopsis development. Quantitative RT-PCR analysis of micro-dissected grain tissues revealed the expression of HvVPE2a, HvVPE2b, HvVPE2d, HvPhS2 and HvPhS3 genes exclusively in the nucellus/nucellar projection. The first increase in cascade of caspase-1, -3, -4, -6 and -8-like activities in the endosperm fraction may be related to programmed cell death in the nucellus and nucellar projection. The second increase of all above caspase-like activities including of caspase-9-like was detected in the maturating endosperm and coincided with expression of HvVPE1 and HvPhS1 genes as well as with degeneration of nuclei in starchy endosperm and transfer cells. The distribution of the TUNEL-positive nuclei, tissues-specific expression of genes encoding proteases with potential caspase activities and cascades of caspase-like activities suggest that each seed tissue follows individual pattern of development and disintegration, which however harmonizes with growth of the other tissues in order to achieve proper caryopsis development.

Highlights

Programmed cell death (PCD) is a highly regulated cellular suicide process essential for growth, development and survival of all eukaryotic organisms
Nuclei of the nucellar cells facing to endosperm were TUNEL-labeled between anthesis and three days after flowering (DAF) (Fig. S1) coinciding with endosperm growth [12]
In the late grain filling phase (16 DAF), TUNEL-positive nuclei were still detected in the nucellar projection and the ventral parts of pericarp (Fig. 1J)

Summary

Introduction

Programmed cell death (PCD) is a highly regulated cellular suicide process essential for growth, development and survival of all eukaryotic organisms. Development of cereal seeds, including barley grains, is largely accompanied by regular cell death. Embryo and endosperm develop within the maternal tissues nucellus, inner and outer integuments, and pericarp, which represent the bulk of the early grain. The nucellar region opposite to the main vascular bundle stays alive and differentiates into the nucellar projection, which functions as a transfer tissue to deliver the assimilates to the endosperm [13]. The growth of the endosperm takes place at the expense of pericarp which largely degenerates till 12 DAF [12] with the exception of the region surrounding the main vascular bundle. Cells of the starchy endosperm undergo PCD during later development [15,16]

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