Genome-Wide Identification and Expression Analysis Unveil the Involvement of the Succinic Semialdehyde Dehydrogenase (SSADH) Gene Family in Banana Low Temperature Stress

Banana (<i>Musa</i> spp.) is susceptible to low-temperature stress and other environmental stresses, which can hinder the growth and development. Succinic semialdehyde dehydrogenase (<i>SSADH</i>) is critical for GABA biosynthesis and plays a crucial role in plants. However, the <i>SSADH</i> genes of bananas have not been studied. This study found 19 <i>MaSSADHs</i>, 18 <i>MbSSADHs</i>, and 18 <i>MiSSADHs</i> from the banana genome. According to the phylogenetic tree, these genes can be categorized into five branches. This study cloned the <i>MaSSADH1-14</i> from banana. The subcellular localization assays of <i>MaSSADH1-14</i> in tobacco leaves confirmed that the presence of <i>SSADH</i> was not only localized mitochondrion but also localized chloroplast. The <i>cis</i>-elements of the <i>SSADH</i> gene family are related to the potential regulation of the banana <i>SSADH</i> gene family; their involvement in diverse stress responses. Transcriptomic data was utilized to examine the effect of <i>MaSSADH</i> genes under cold stress in bananas. The results of RT-qPCR were consistent with transcriptome data. These results showed that most <i>MaSSADHs</i> are passively responsive to low-temperature treatment. In addition, transient overexpression of <i>MaSSADH1-14</i> in <i>Nicotiana benthamiana</i> leaves resulted in the content of GABA increasing, indicating that <i>MaSSADH1-14</i> may be involved in the accumulation of GABA of banana. Collectively, these results improve knowledge of the <i>SSADH</i> gene family in banana and establish a basis for comprehending its biological roles in response to low temperatures.