Biology subjects

Backhouse, D.

Publications and source records attributed to Backhouse, D..

3 recordsLinked to original sources

bioRxiv2023

Inhibition of auxin biosynthesis in early rice grains leads to extensive post-fertilisation grain abortion

In spite of its abundant presence in rice grains, auxin functions during grain development are not understood well. Absence of grain-specific auxin biosynthesis mutants in rice further limits our understanding in this respect. Here, we report a chemical biology approach to inhibit auxin biosynthesis specifically in early rice grains as well as its subsequent effects on final grain yield. Exogenous application of two auxin biosynthesis inhibitors, namely L-kynurenine (L-Kyn) and 4-phenoxyphenylboronic acid (PPBo), to spikelets daily from three to ten days after pollination (DAP) significantly reduced grain levels of indole-3-acetic acid (IAA), the predominant in planta auxin. The inhibitor-treated panicles showed extensive post-fertilisation seed abortion, leading to drastic reduction in total panicle weight at maturity. Locally synthesised auxin during early grain development may therefore play a crucial role in grain retention. This chemical biology approach can be an easy and cost-effective way to study auxin biosynthesis and signalling during grain development in rice and possibly other cereal crops. HighlightAuxin synthesised in early rice grains may play a crucial role in grain retention.

plant biology↗

bioRxiv2021

Localised expression of OsIAA29 suggests a key role for auxin in regulating development of the dorsal aleurone of early rice grains

Endosperm of rice and other cereals accumulates high concentrations of the predominant in planta auxin, indole-3-acetic acid (IAA) during early grain development. However, IAA signalling and function during endosperm development are poorly understood. Here, we report that OsYUC12 (an auxin biosynthesis gene) and OsIAA29 (encoding a non-canonical AUX/IAA) are both expressed exclusively in grains, reaching a maximum 5 to 6 days after pollination. OsYUC12 expression is localized in the aleurone, sub-aleurone and embryo, whereas OsIAA29 expression is restricted to a narrow strip in the dorsal aleurone, directly under the vascular bundle. Although rice has been reported to lack endosperm transfer cells (ETCs), this region of the aleurone is enriched with sugar transporters and is likely to play a key role in apoplastic nutrient transfer, analogous to ETCs in other cereals. OsIAA29 has orthologues only in grass species; expression of which is also specific to early grain development. OsYUC12 and OsIAA29 are temporally co-expressed with two genes (AL1 and OsPR602) previously linked to the development of dorsal aleurone or ETCs. Also up regulated at the same time are a cluster of MYB-related genes (designated OsMRPLs) homologous to ZmMRP-1, which regulates maize ETC development. Wheat homologues of ZmMRP-1 are also expressed in ETCs. Although previous work has suggested that other cereals do not have orthologues of ZmMRP-1, our work suggests OsIAA29 and OsMRPLs and their homologues in other grasses are part of an auxin-regulated, conserved signalling network involved in the differentiation of cells with ETC-like function in developing cereal grains. Main ConclusionNon-canonical AUX/IAA protein, OsIAA29, and ZmMPR-1 homologues, OsMRPLs, are part of an auxin-related signalling cascade operating in the dorsal aleurone during early rice grain development.

plant biology↗

bioRxiv2020

Expression of TaTAR2.3-1B, TaYUC9-1 and TaYUC10 correlates with auxin and starch content of developing wheat grains

The role of auxin in developing grains of wheat (Triticum aestivum) is contentious with contradictory reports indicating either positive or negative effects of IAA (indole-3-acetic acid) on grain size. In addition, the contributions to the IAA pool from de novo synthesis via tryptophan, and from hydrolysis of IAA-glucose are unclear. Here we describe the first comprehensive study of tryptophan aminotransferase and indole-3-pyruvate mono-oxygenase expression during wheat grain development from 5 to 20 days after anthesis. A comparison of expression data with measurements of endogenous IAA via combined liquid chromatography-tandem mass spectrometry with heavy isotope labelled internal standards indicates that TaTAR2.3-1B, TaYUC9-A1, TaYUC9-B, TaYUC9-D1, TaYUC10-A and TaYUC10-D are primarily responsible for IAA production in developing grains. Furthermore, we show that IAA synthesis is controlled by genes expressed specifically in developing wheat grains as has already been reported in rice (Oryza sativa) and maize (Zea mays). Our results cast doubt on the proposed role of THOUSAND-GRAIN WEIGHT gene, TaTGW6, in promoting larger grain size via negative effects on grain IAA content. The work on TaTGW6 has overlooked the contribution of the dominant IAA biosynthesis pathway. Although IAA synthesis occurs primarily in the endosperm of wheat grains, we show that the TaYUC9-1 group is also strongly expressed in the embryo. Within the endosperm, TaYUC9-1 expression is highest in aleurone and transfer cells, supporting data from other cereals suggesting that IAA has a key role in differentiation of these tissues.

plant biology↗