SPOTTED-LEAF7 targets the gene encoding β-galactosidase9, which functions in rice growth and stress responses

Abstract

β-Galactosidases (Bgals) remove terminal β-D-galactosyl residues from the non-reducing ends of β-D-galactosides and oligosaccharides. Bgals are present in bacteria, fungi, animals, and plants and have various functions. Despite many studies on the evolution of BGALs in plants, their functions remain obscure. Here, we identified rice (Oryza sativa) β-galactosidase9 (OsBGAL9) as a direct target of the heat stress-induced transcription factor SPOTTED-LEAF7 (OsSPL7), as demonstrated by protoplast transactivation analysis and yeast one-hybrid and electrophoretic mobility shift assays. Knockout plants for OsBGAL9 (Osbgal9) showed short stature and growth retardation. Histochemical ß-glucuronidase (GUS) analysis of transgenic lines harboring an OsBGAL9pro:GUS reporter construct revealed that OsBGAL9 is mainly expressed in internodes at the mature stage. OsBGAL9 expression was barely detectable in seedlings under normal conditions but increased in response to biotic and abiotic stresses. Ectopic expression of OsBGAL9 enhanced resistance to the rice pathogens Magnaporthe oryzae and Xanthomonas oryzae pv. oryzae, as well as tolerance to cold and heat stress, while Osbgal9 mutant plants showed the opposite phenotypes. OsBGAL9 localized to the cell wall, suggesting that OsBGAL9 and its plant putative orthologs likely evolved functions distinct from those of its closely related animal enzymes. Enzyme activity assays and analysis of the cell wall composition of OsBGAL9 overexpression and mutant plants indicated that OsBGAL9 has activity toward galactose residues of arabinogalactan proteins (AGPs). Our study clearly demonstrates a role for a member of the BGAL family in AGP processing during plant development and stress responses.

Genome-Wide Identification and Expression Analysis of Beta-Galactosidase Family Members in Chinese Bayberry (Myrica rubra)

“…In rice, the functional analysis of knockout plants for OsBGAL9 underscored the pivotal role of BGALs. The observed phenotype, marked by short stature and growth retardation, highlights the significance of OsBGAL9 in the regulation of rice plant growth and development [30]. The conservation of all MrBGALs was generally high, with the exception of MrChr3G28800, which contained the Glyco_hydro_35 domain motif.…”

“…The protein subcellular location of the BGAL in melon and Arabidopsis showed that they were mainly located in extracellular space (cell wall) [11]. The BGAL play significant roles throughout a plant's lifecycle, influencing plant growth and development, including fruit softening [22][23][24][25][26], fruit development and ripening [19,27,28], seed germination [29], stress responses [30,31], and root development [32]. Furthermore, β-galactosidase is believed to expedite fruit softening [33].…”

New insights into QTNs and potential candidate genes governing rice yield via a multi-model genome-wide association study

“…LOC_Os12G24170 is a precursor of beta-galactosidase enzyme (BGAL) that mediates the physiological process of seed germination through cross talks among GA and Abscisic acid (ABA) to determine grain yield in rice [ 3 ]. Knockout studies revealed that BGAL9 regulates different physiological functions and stress responses in rice [ 108 ]. Transcriptomics studies very well implied the upregulation of OsBAGL1, OsBAGL4, OsBAGL8 and OsBAGL11 genes during seed germination and their influence on plant growth and development [ 109 ].…”