Analysis of TCP Transcription Factors Revealed Potential Roles in Plant Growth and Fusarium oxysporum f.sp. cubense Resistance in Banana (cv. Rasthali).

The TCP transcription factor gene family is highly conserved among the plant species. It plays a major role in the regulation of flower symmetry, cell division, and development of leaf, fibre, and nodule in the plants by controlling the synthesis of various plant hormones. Banana is a major staple crop in the world. However, Fusarium oxysporum f. sp. cubense (Foc) infection is a major threat to banana production. The role of TCP gene family during the Foc infection is not explored till now. Herein, a total of 27 non-redundant TCP (MaTCP) gene sequences were retrieved from the banana genome and analysed for structural characteristics, phylogenetic correlation, subcellular, and chromosomal localizations. Phylogenetic analysis showed that the MaTCP proteins were highly conserved among different species and found to be the closest relative of the Oryza sativa and Zea mays. Promoter analysis of the TCP sequences showed that the cis-acting regulatory elements are associated with various stresses and environmental and hormonal signals. The higher transcript accumulation in developing tissues (fruit finger, leaves, and stem) than of mature tissues (peel and pulp) showed a significant role of MaTCP in banana (cv. Rasthali) growth and development. Further, higher expression of the certain MaTCPs in Foc race 1-infected root (MaTCP2, MaTCP4, MaTCP6) and leaf (MaTCP9 and MaTCP11) tissues of Rasthali indicated their promising role during Fusarium infection. This study will underpin the facet of TCP transcription factors on the development of biotic (Foc) stress resistance in banana.

Induction of Ced9 mediated anti-apoptosis in commercial banana cultivar Rasthali for stable resistance against Fusarium wilt.

Anti-apoptotic gene Ced-9 enhanced resistance against Fusarium oxysporum f. sp. cubense (Foc) in the susceptible banana cultivar Rasthali by arresting tissue necrosis. The embryogenic cell suspension of banana cultivar Rasthali was stably transformed with Ced-9 gene and transformed lines were regenerated independently. The putative transgenic lines were analyzed with PCR using gene primers and further subjected to Southern blot to estimate copy number. The root-challenge bioassay with Foc showed 17-51% Vascular Discoloration Index in independent transformants compared to untransformed banana cv Rasthali (98% VDI). Four transgenic events showed a higher level of resistance over a period of 6 months. Overcoming tissue necrosis is the most ideal method to avoid Fusarium multiplication and spread in banana. Oxidative stress-induced cell necrosis is prevented by the activation of antiapoptotic pathways by Ced-9 and is proving to be an effective method to control this dreaded disease. This is the first report from India on the generation of transgenic banana cultivar Rasthali expressing antiapoptotic Ced-9 gene for resistance to Fusarium wilt.

Deployment of Stacked Antimicrobial Genes in Banana for Stable Tolerance Against Fusarium oxysporum f.sp. cubense Through Genetic Transformation.

Enhanced tolerance to wilt disease (Fusarium oxysporum f.sp. cubense) was achieved in banana variety Rasthali (AAB) by the transformation of embryogenic cells with two antimicrobial genes viz., Ace-AMP1 and pflp using Agrobacterium mediated transformation. The transgene copy numbers in stable transformants were confirmed by Southern analysis. The expression of stacked genes in the transgenic lines was validated by RT-PCR as well as Northern analysis. Bioassay using Foc race 1 in pot culture experiments demonstrated enhanced tolerance after 180 days of planting. Two independent transformants showed 10-20% Vascular Discoloration Index compared to untransformed banana cv. Rasthali (96%). The stacked lines revealed higher activity of Super Oxide Dismutase and Peroxidase compared to untransformed control which depicted higher tolerance to oxidative stress caused by Foc infection.