ASHS 2024 Conference

Rootstocks play a crucial role in shaping plant growth and vigour, driven by a complex interplay of physiological, molecular, and genetic factors. Aquaporins (AQPs), as key water transport proteins, are emerging as pivotal component in understanding rootstock-mediated vigour. However, evidence for rootstock effects in macadamia remains limited with no exploration into the mechanisms of rootstock-mediated vigour control, hindering progress in rootstock development for this crop. In this study, we aimed to explore the role of AQPs by conducting a genome-wide investigation on whole genome sequence of Macadamia integrifolia (‘HAES741’). This study identified 37 putative macadamia AQP (miAQP) genes belonging to 5 different sub-families including 11 plasma membrane intrinsic proteins, 10 tonoplast intrinsic proteins, 10 Nod26-like intrinsic proteins, 2 small and basic proteins and 6 X-intrinsic proteins. miAQP genes are unevenly distributed across 11 chromosomes with chromosome 7 possessing the most genes. To investigate the differential expression of plasma membrane intrinsic proteins (PIPs), in high- and low-vigour rootstocks, root, leaf, and stem tissues were collected from trees with a single scion ‘HAES741’ grafted on to 7 different rootstock genotypes . RNA from tissue samples were extracted by a modified CTAB RNA extraction protocol using the Zymo-spin™ IICR Column. RNA quality and quantity was checked via nano spectrophotometer and gel electrophoresis. Primer pairs for 11 PIP genes and 2 housekeeping genes (ACT and EF1b) were designed using Primer BLAST in NCBI. RNA samples were subjected to a real time quantitative RT-PCR. The tissue specific expression data will be analysed to observe differential expressions, if any, between high and low vigour rootstocks and scions. Differential expression patterns reveal the PIP genes associated with vigour control. The correlation between gene expression levels and rootstock vigour provides better understanding on the intrinsic molecular mechanism vigour regulation in macadamia. Moreover, comparative analysis of PIP gene expression between rootstock and scion can provide insights into the rootstock-scion interactions. Overall, results from this study offer a better understanding of the molecular basis of rootstock-mediated vigour control with implications for rootstocks development and orchard optimization in macadamia.