Identification and molecular evolution of the GLX genes in 21 plant species: a focus on the Gossypium hirsutum

Cloning and Functional Analysis of Glyoxalase I Gene BrGLYI 13 in Brassica rapa L

Glyoxalase I (GLYI) is a key enzyme that detoxifies methylglyoxal, a toxic byproduct of glycolysis, and is essential for plant pollination. However, the genome-wide identification and functional analysis of GLYI in Brassica rapa L. (B. rapa) remain limited. This study identified 17 BrGLYI genes (BrGLYI1-BrGLYI17) from the B. rapa genome. The self-compatible line 039-1 and the self-incompatible line GAU-28-5 were used as experimental materials, and Real-Time Quantitative Reverse Transcription PCR (RT-qPCR) was performed to examine the effect of BrGLYI genes on self-compatibility in winter B. rapa. Preliminary results showed that BrGLYI13 exhibited significant tissue specificity, with higher expression in the flowers of 039-1 compared to GAU-28-5. The open reading frame of BrGLYI13 (852 bp) was cloned from both 039-1 and GAU-28-5 cDNA, with no base mutations observed between the two lines. RT-qPCR revealed higher BrGLYI13 expression in the stigma of 039-1 compared to GAU-28-5. Based on the functional conservation and sequence homology, BrGLYI13 is speculated to play a similar role to that of AtGLYI3 in methylglyoxal detoxification and stress response. Furthermore, the knockout of AtGLYI3 resulted in reduced silique lengths and seed numbers. These findings suggest that BrGLYI13 is involved in the self-compatibility response in B. rapa and promotes the silique length and seed number in the Arabidopsis mutant, providing a basis for further research on the mechanisms of self-compatibility in B. rapa.

A translation proofreader of archaeal origin imparts multi-aldehyde stress tolerance to land plants

Aldehydes, being an integral part of carbon metabolism, energy generation, and signalling pathways, are ingrained in plant physiology. Land plants have developed intricate metabolic pathways which involve production of reactive aldehydes and its detoxification to survive harsh terrestrial environments. Here, we show that physiologically produced aldehydes, i.e., formaldehyde and methylglyoxal in addition to acetaldehyde, generate adducts with aminoacyl-tRNAs, a substrate for protein synthesis. Plants are unique in possessing two distinct chiral proofreading systems, D-aminoacyl-tRNA deacylase1 (DTD1) and DTD2, of bacterial and archaeal origins, respectively. Extensive biochemical analysis revealed that only archaeal DTD2 can remove the stable D-aminoacyl adducts on tRNA thereby shielding archaea and plants from these system-generated aldehydes. Using Arabidopsis as a model system, we have shown that the loss of DTD2 gene renders plants susceptible to these toxic aldehydes as they generate stable alkyl modification on D-aminoacyl-tRNAs, which are recycled only by DTD2. Bioinformatic analysis identifies the expansion of aldehyde metabolising repertoire in land plant ancestors which strongly correlates with the recruitment of archaeal DTD2. Finally, we demonstrate that the overexpression of DTD2 offers better protection against aldehydes than in wild type Arabidopsis highlighting its role as a multi-aldehyde detoxifier that can be explored as a transgenic crop development strategy.

Pyramiding D-lactate dehydrogenase with the glyoxalase pathway enhances abiotic stress tolerance in plants

Methylglyoxal is a common cytotoxic metabolite produced in plants during multiple biotic and abiotic stress. To mitigate the toxicity of MG, plants utilize the glyoxalase pathway comprising glyoxalase I (GLYI), glyoxalase II (GLYII), or glyoxalase III (GLYIII). GLYI and GLYII are the key enzymes of glyoxalase pathways that play an important role in abiotic stress tolerance. Earlier research showed that MG level is lower when both GLYI and GLYII are overexpressed together, compared to GLYI or GLYII single gene overexpressed transgenic plants. D-lactate dehydrogenase (D-LDH) is an integral part of MG detoxification which metabolizes the end product (D-lactate) of the glyoxalase pathway. In this study, two Arabidopsis transgenic lines were constructed using gene pyramiding technique: GLYI and GLYII overexpressed (G-I + II), and GLYI, GLYII, and D-LDH overexpressed (G-I + II + D) plants. G-I + II + D exhibits lower MG and D-lactate levels and enhanced abiotic stress tolerance than the G-I + II and wild-type plants. Further study explores the stress tolerance mechanism of G-I + II + D plants through the interplay of different regulators and plant hormones. This, in turn, modulates the expression of ABA-dependent stress-responsive genes like RAB18, RD22, and RD29B to generate adaptive responses during stress. Therefore, there might be a potential correlation between ABA and MG detoxification pathways. Furthermore, higher STY46, GPX3, and CAMTA1 transcripts were observed in G-I + II + D plants during abiotic stress. Thus, our findings suggest that G-I + II + D has significantly improved MG detoxification, reduced oxidative stress-induced damage, and provided a better protective mechanism against abiotic stresses than G-I + II or wild-type plants.