MaSERK1 Gene Expression Associated with Somatic Embryogenic Competence and Disease Resistance Response in Banana (Musa spp.)

A banana somatic embryogenesis receptor-like kinase (SERK) gene, designated as MaSERK1, was isolated from Musa acuminata cv. Mas (AA). It encoded a protein of 628 amino acids with above 82% identities to reported SERKs of coconut, rice, maize, Arabidopsis, carrot, and Medicago truncatula. MaSERK1 was expressed weakly in male flower clusters, but not in male flower-derived nonembryogenic calli, but it was highly expressed in male flower-derived embryogenic calli and embryogenic cell suspensions (ECS). During subculture of ECS, MaSERK1 expression and frequency of somatic embryogenesis were influenced by the duration of subculture, wherein expression decreased within 0 to 6 days of subculture, increased to highest levels at 12 days following subculture, and dropped thereafter. The frequency of somatic embryogenesis of ECS positively correlated with MaSERK1 transcript levels. Moreover, MaSERK1 expression in leaves of Musa paradisiaca L. cv. Dongguan Dajiao (ABB), known to be resistant to Fusarium oxysporum f. sp. cubense race 4 (FOC race 4), was induced by exogenous salicylic acid (SA) or inoculation with FOC race 4. However, MaSERK1 expression levels in leaves of Mucus spp. cv. Pisang awak (ABB), known to be susceptible to FOC race 4, did not change following either treatment. These results suggested that MaSERK1 not only could serve as a molecular marker for banana somatic embryogenesis, but also played a role in disease resistance response in banana.