Molecular analysis of somatic embryogenesis through proteomic approach and optimization of protocol in recalcitrant Musa spp.

Somatic embryogenesis (SE) is a complex stress related process regulated by numerous biological factors. SE is mainly applicable to mass propagation and genetic improvement of plants through gene transfer technology and mutation breeding. In banana, SE is highly genome dependent as the efficiency varies with cultivars. To understand molecular mechanism of SE, proteomics approach was carried out to identify genes responsible for embryogenic calli (EC) induction, regeneration and germination of somatic embryos (se) in cv. Rasthali (AAB). In total, 70 spots were differentially expressed in various developmental stages of SE. Of which, 16 were uniquely expressed and 17 were highly abundant in EC than nonembryogenic calli and explant and four spots were also uniquely expressed in germinating se. Functional annotation of identified proteins revealed that calcium signaling along with stress and endogenous hormones related proteins played a vital role in EC induction and germination of se. Thus based on the outcome, callus induction media was modified and tested in five cultivars. In cv. Grand Naine (AAA), increased concentration of 3- IAA and tryptophan recorded highest EC induction of 24.28% while Red Banana with similar genome showed 18.96% in kinetin supplemented media. Similarly, in cultivars Monthan and Karpuravalli with ABB genome showed maximum EC induction in tryptophan supplemented media (8.54%) and CaCl2 enriched media (17.34%) respectively. In cv. Neypoovan (AB), higher concentration of tryptophan induced more EC. These results illustrated that EC formation is genome as well as cultivar dependent. Simultaneously, germination media was modified to induce proteins responsible for germination. In cv. Rasthali, media supplemented with 10 mM CaCl2 showed maximum increase in germination (51.79%) over control. Thus present study revealed that media modification based on proteomic studies can induce SE in recalcitrant cultivars and also enhance germination in cultivars amenable for SE.