Genome-Wide HMG Family Investigation and Its Role in Glycoalkaloid Accumulation in Wild Tuber-Bearing Solanum commersonii

Abstract

Steroidal glycoalkaloids (SGAs) are a class of nitrogen-containing glycosides occurring in several plant families and biosynthesized through a specific pathway. HMG-CoA reductase is the first enzyme of this pathway, and its transcription can be regulated by biotic and abiotic stressors and even in a tissue-specific manner. This study aimed to characterize the HMG genes family in a tuber-bearing potato species, Solanum commersonii, using transcriptional and functional approaches. Our results provided evidence that four ScHMGs with different tissue-specificities represent the HMG gene family in S. commersonii and that they originated from ScHMG1 through segmental duplications. Phylogenetic analysis suggests that ScHMG1 is the direct ortholog of AtHMG1, which is associated with SGAs accumulation in plants. Its overexpression in S. commersonii revealed that this gene plays a key role in the accumulation of glycoalkaloids regulating the production of dehydrocommersonine.

Metabolomic and transcriptomic analyses identify external conditions and key genes underlying high levels of toxic glycoalkaloids in tubers of stress-sensitive potato cultivars

“…The increased SGA levels in leafs from transgenic potato plants overexpressing StHMGR1 and StTAM2 indicate that induced expression of one single key SGA gene can be sufficient to increase SGA synthesis. The increased leaf SGA levels in our HMGR1 -overexpessing transformants are well in agreement with other reports on HMGR1-overexpressing potatoes ( Ginzberg et al., 2012 ; Moehninsi et al., 2020 ; Villano et al., 2020 ) and suggest a limiting function of the enzyme. The effect of TAM2 overexpression on SGA levels in table potatoes has not been investigated directly, although Nakayazu et al.…”

Solanum steroidal glycoalkaloids: structural diversity, biological activities, and biosynthesis

“…The integrated pathway related to SGA biosynthesis includes the cytosolic mevalonate pathway and a multi-step pathway for the production of cycloartenol, cholesterol, and core SGA, comprising the synthesis and glycosylation of the steroidal alkaloid aglycone. 1,3,9,15,31–35,116,117 This biosynthetic process involves a large number of genes (Fig. 11); for example, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) catalyzes the MVA formation.…”