Biology subjects

Gresshoff, P. M.

Publications and source records attributed to Gresshoff, P. M..

3 recordsLinked to original sources

bioRxiv2025

The biofuel producing legume tree, Pongamia pinnata, offers strong potential for carbon sequestration

Pongamia pinnata (Linn.) Pierre, also called Millittia pinnata or Indian beach, is a fast-growing legume tree that has gained considerable attention for its potential as a feedstock for biofuel. In this study, we assessed the growth characteristics and carbon sequestering potential of Pongamia grown under sub-tropical environments. At two different sites located in Queensland, Australia, Pongamia was found to produce considerable biomass, even when planted in nutrient-poor environments having low soil organic carbon. The seedlings planted were all derived directly from genetically diverse, yet related seed. Variability observed in growth appeared to be associated with the mother tree from which the seeds were sourced, underscoring the importance of planting elite genetic material for commercial purposes. Pongamia is known to be drought tolerant, with findings here demonstrating that even young seedlings have this characteristic. Collectively, our findings indicate that Pongamia can grow quickly, reaching a biomass of 13-19 kg over 3-4 years in our studies, and sequester high quantities of carbon, at 2.9 to 4.0 t of carbon per ha (assuming a tree density of [~]450/ha), even when planted in suboptimal growing conditions on marginal, nutrient-poor lands.

plant biology↗

bioRxiv2020

Shoot-derived miR2111 controls legume root and nodule development

Legumes control their nodule numbers through the Autoregulation Of Nodulation (AON). Rhizobia infection stimulates the production of root-derived CLE peptide hormones that are translocated to the shoot where they regulate a new signal. We used soybean to demonstrate that this shoot-derived signal is miR2111, which is transported via phloem to the root where it targets transcripts of Too Much Love (TML), a negative regulator of nodulation. Shoot perception of rhizobia-induced CLE peptides suppresses miR2111 expression, resulting in TML accumulation in roots and subsequent inhibition of nodule organogenesis. Feeding synthetic mature miR2111 via the petiole increased nodule numbers per plant. Likewise, elevating miR2111 availability by over-expression promoted nodulation, while target mimicry of TML induced the opposite effect on nodule development in wild-type plants and alleviated the supernodulating and stunted root growth phenotypes of AON-defective mutants. Additionally, in non-nodulating wild-type plants, ectopic expression of miR2111 significantly enhanced lateral root emergence with a decrease in lateral root length and average root diameter. In contrast, hairy roots constitutively expressing the target mimic construct exhibited reduced lateral root density. Overall, these findings demonstrate that miR2111 is both the critical shoot-to-root factor that positively regulates root nodule development, and also acts to shape root system architecture via orchestrating the degree of root branching, as well as the length and thickness of lateral roots.

plant biology↗

bioRxiv2020

Characterisation of Medicago truncatula CLE34 and CLE35 in nodulation control

Legume plants form a symbiosis with N2-fixing soil rhizobia, resulting in new root organs called nodules that enable N2-fixation. Nodulation is a costly process that is tightly regulated by the host through Autoregulation of Nodulation (AON) and nitrate-dependent regulation of nodulation. Both pathways require legume-specific CLAVATA/ESR-related (CLE) peptides. Nitrogen-induced nodulation-suppressing CLE peptides have not previously been characterised in Medicago truncatula, with only rhizobia-induced MtCLE12 and MtCLE13 identified. Here, we report on novel peptides MtCLE34 and MtCLE35 in nodulation control pathways. The nodulation-suppressing CLE peptides of five legume species were classified into three clades based on sequence homology and phylogeny. This approached identified MtCLE34 and MtCLE35 and four new CLE peptide orthologues of Pisum sativum. Whereas MtCLE12 and MtCLE13 are induced by rhizobia, MtCLE34 and MtCLE35 respond to both rhizobia and nitrate. MtCLE34 was identified as a pseudogene lacking a functional CLE-domain. Overexpression of MtCLE12, MtCLE13 and MtCLE35 inhibits nodulation. Together, our findings indicate that MtCLE12 and MtCLE13 have a distinct role in AON, while MtCLE35 regulates nodule numbers in a rhizobia- and nitrate-dependent manner. MtCLE34 likely had a similar role to MtCLE35 but its function was lost due to a nonsense mutation resulting in the loss of the mature peptide.

plant biology↗