| Banana is a monocotyledonous large perennial herb belonging to Musaceae Musa,widely grown in tropical and subtropical regions,and is an important fruit and food crop.However,the soil in tropical and subtropical regions is acidic,and the rainy climate causes serious loss of magnesium in the soil,causing bananas to face the threat of magnesium deficiency,which seriously affects the yield and quality of bananas.Therefore,the low magnesium stress has become an urgent problem to be solved for banana.The TCP gene family is sensitive to the ratio of red light to far-red light and high light stress,but there is no report on the expression pattern of the TCP gene family under banana low magnesium stress.In this paper,by measuring the physiological indexes of Brazilian banana seedlings（Musa acuminate,AAA group,cv.Baxijiao,Cavendish sub-group）under low magnesium stress,such as the magnesium content,chlorophyll content,and net photosynthetic rate.And the response was analyzed from the physiological level which was under the low magnesium stress.At the same time,based on banana A genome and expression profile data,the expression pattern of TCP gene family under low magnesium stress was analyzed,and the mechanism of banana response to low magnesium stress was analyzed at the molecular level.The main results are as follows:（1）Under low magnesium stress,banana leaves have phenotypic characteristics of yellowing from the edge of the leaf to the veins,and there are differences in the yellowing characteristics of the edge,middle,and interior of the leaves.The results showed that under low-magnesium treatment,CO2 fixation,chlorophyll content,net photosynthetic rate decreased in banana L9 leaves,and P element content increased.It shows that the photosynthetic capacity of bananas decreases under low magnesium stress.（2）Transcriptomics analysis and sequencing were performed on the edges,middle,and interior of L9 leaves under the condition of magnesium deficiency in bananas.The combination of GO and KEGG enrichment of differential genes showed that the response of bananas to magnesium deficiency stress includes a variety of metabolic pathways,especially chlorophyll synthesis and degradation pathways.Under magnesium deficiency,the expression of chlorophyll synthesis-related genes CHLI,CHLM and CHLG was down-regulated,while the expression of chlorophyll degradation-related SGR gene was up-regulated.In summary,both RNA-seq and RT-PCR indicate that chlorophyll synthesis and degradation pathways are involved in the response of bananas to magnesium deficiency stress.（3）A total of 48 banana TCP gene family members have been identified in bananas.According to the conservative structure of the protein sequence,it can be divided into two categories,ClassⅠand ClassⅡ,and ClassⅡcan be divided into two categories（CYC/TB1 and CIN）.The gene family members in CYC/TB1 are not expressed under low magnesium stress.Or the expression level is very low.The expressions of Ma06＿g29190and Ma11＿g14160 genes in the TCP gene family were significantly up-regulated in the treatment of low magnesium,indicating that the TCP transcription factor gene family may be involved in the response of bananas to magnesium deficiency.In summary,low magnesium stress caused the yellowing of banana leaves and the decline of photosynthetic capacity;and the TCP transcription factor gene family participated in the banana’s response to magnesium deficiency.The research results lay a foundation for further revealing the genetic evolution and molecular functions of bananas,and provide references for related research on plant resistance to low magnesium stress. |
