MrERF, MrbZIP, and MrSURNod of Medicago ruthenica Are Involved in Plant Growth and Abiotic Stress Response

Abstract

Abiotic stresses affect plant growth and productivity. The outstanding stress resistance of Medicago ruthenica makes it a desirable gene resource to improve the stress tolerance of other plants. The roles of three differently expressed genes [(DEGs) (MrERF, MrbZIP, and MrSURNod)] from M. ruthenica in stress resistance have not been fully elucidated. Therefore, we constructed their expression vectors, transformed them into tobacco, and subjected transgenic lines to abiotic stresses. Through comprehensive bioinformatics, transcriptomic, morphological, and physiological analyses of transgenic lines, we have revealed the critical role of these three DEGs in plant growth and abiotic stress response. The upregulation of genes enhanced the germination rate, biomass, root length number, etc. Additionally, the accumulation of osmolytes increased the activity of antioxidant enzymes. These genes are also associated with improved seed yield, increased branching, and early flowering, thereby shortening the growth period. Potentially, this is one of the ways for tobacco to cope with stress. Furthermore, the resistance of transgenic tobacco expressing MrERF or MrbZIP was better than that with MrSURNod. MrERF and MrbZIP can improve drought and salt tolerance of plants, whereas MrSURNod is beneficial in improving drought and cold resistance. Moreover, MrERF or MrbZIP can promote root elongation and increase the root number, whereas MrSURNod mainly promotes root elongation. This may be the reason why stress resistance conferred by MrSURNod is weaker than that associated with the other two genes. Overall, MrERF, MrbZIP, and MrSURNod positively modulate plant growth and stress tolerance.

Crop Wild Relatives: A Valuable Source of Tolerance to Various Abiotic Stresses

“…M. ruthenica is thought to be a rather uncommon species among Medicago species that is highly adapted to stressful conditions, and whose prospective applicability is favorably assessed in low-input environments. The roles of differentially expressed abiotic stress-related genes, such as the AP2/ERF family, MYB/MYB-related family, bZIP, bHLH, and WRKY from M. ruthenica in conferring stress tolerance have not been fully elucidated [ 95 , 96 ]. These genes play important roles in many different regulation mechanisms of diverse abiotic stresses.…”

“…Two differentially expressed genes (DEGs) (MrERF, MrbZIP ) from M. ruthenica have not yet been thoroughly characterized in terms of their functions in salt tolerance. Wu et al [ 95 ] demonstrated the transgenic lines of tobacco over-expressing these genes grew more successfully than wild types exhibiting greater height, more branches, and earlier flowering. Additionally, compared to wild type tobacco, the seed yield of transgenic tobacco was considerably higher.…”

“…A total of 894 genes were identified that responded to cold stress. Expressions of MrUN10866, MrUN33504, MrUN37588 , and MrUN40182 were induced by cold stress [ 95 ]. Numerous transcription factors (TFs) have been identified, and they all play crucial roles in how plants react to abiotic stressors, such as cold, including AP2/ERF, bHLH, MYB, WRKY, C2H2, and NAC.…”

“…The AP2/ERF TF family, whose members have been extensively characterized for their involvement in cold tolerance, was the largest. This finding suggests these genes play a crucial role in the abiotic stress response, and they may be utilized in breeding alfalfa [ 95 ]. The wild Medicago species that presented tolerance in the above-mentioned abiotic stresses are presented in Table 1 .…”