Hormonal Influences on Pod-Seed Intercommunication during Pea Fruit Development.

Mark Bal,Lars Østergaard

doi:10.3390/genes13010049

Abstract

Angiosperms (from the Greek “angeion”—vessel, and “sperma”—seed) are defined by the presence of specialised tissue surrounding their developing seeds. This tissue is known as the ovary and once a flower has been fertilised, it gives rise to the fruit. Fruits serve various functions in relation to the seeds they contain: they often form tough physical barriers to prevent mechanical damage, they may form specialised structures that aid in dispersal, and they act as a site of nutrient and signal exchange between the parent plant and its offspring. The close coordination of fruit growth and seed development is essential to successful reproduction. Firstly, fertilisation of the ovules is required in most angiosperm species to initiate fruit growth. Secondly, it is crucial that seed dispersal facilitated by, e.g., fruit opening or ripening occurs only once the seeds have matured. These highly coordinated events suggest that seeds and fruits are in close communication throughout development and represent a classical problem of interorgan signalling and organismic resource allocation. Here, we review the contribution of studies on the edible, unicarpellate legume Pisum sativum to our understanding of seed and fruit growth coregulation, and propose areas of new research in this species which may yield important advances for both pulse agronomy and natural science.

Highlights

How multicellular organisms regulate the development of their reproductive structures, and how this process intersects with the development and growth of their offspring, are areas of active research in molecular biology
As the pea mutant lacking the auxin biosynthesis gene TRYPTOPHAN AMINOTRANSFERASE RELATED2 (TAR2) had reduced levels of 4-Cl-IAA [15], and because chlorinated tryptophan was detected in pea tissues [15], it is currently thought that 4-Cl-IAA is produced from 4-Cl tryptophan, which is itself generated from tryptophan or a tryptophan precursor by an unknown halogenating enzyme
Using the DR5::GUS reporter in pea revealed increased auxin signalling in pea pods treated with 4-Cl-IAA compared to equimolar IAA. These results suggest that 4-Cl-IAA at least partially functions through the canonical auxin signalling pathway mediated by the TIR1/AFB auxin receptors

Summary

Introduction

How multicellular organisms regulate the development of their reproductive structures, and how this process intersects with the development and growth of their offspring, are areas of active research in molecular biology. Failure of the offspring to develop may result in the spontaneous abortion of the entire reproductive organ, which prevents further investment into non-viable fruit. This can, in turn, free up resources for reallocation into other, viable developing reproductive structures, or into the survival of the parent plant as a whole. Deciphering the seed/fruit molecular conversation that regulates pea reproductive development may lead to the discovery of the different signalling systems relative to Arabidopsis, but perhaps to important advancements in legume agronomy in general, as pod shape varies between crop accessions [4]. We review research on seed/pod intercommunication in pea, present outstanding questions, and provide avenues for future research

Pod Elongation

Activity of 4-Chloroindole-3-acetic Acid in Promoting Pod Elongation

Secondary Hormonal Regulation of Pod Elongation

Seed Filling

Findings

Conclusions and Future Perspectives