NnABI4-Mediated ABA Regulation of Starch Biosynthesis in Lotus (Nelumbo nucifera Gaertn)

Abstract

Starch is an important component in lotus. ABA is an important plant hormone, which plays a very crucial role in regulating plant starch synthesis. Using ‘MRH’ as experimental materials, the leaves were sprayed with exogenous ABA before the rhizome expansion. The results showed that stomatal conductance and transpiration rate decreased while net photosynthetic rate increased. The total starch content of the underground rhizome of lotus increased significantly. Meanwhile, qPCR results showed that the relative expression levels of NnSS1, NnSBE1 and NnABI4 were all upregulated after ABA treatment. Then, yeast one-hybrid and dual luciferase assay suggested that NnABI4 protein can promote the expression of NnSS1 by directly binding to its promoter. In addition, subcellular localization results showed that NnABI4 encodes a nuclear protein, and NnSS1 protein was located in the chloroplast. Finally, these results indicate that ABA induced the upregulated expression of NnABI4, and NnABI4 promoted the expression of NnSS1 and thus enhanced starch accumulation in lotus rhizomes. This will provide a theoretical basis for studying the molecular mechanism of ABA regulating starch synthesis in plant.

Integrated mRNA and Small RNA Sequencing Reveals a microRNA Regulatory Network Associated with Starch Biosynthesis in Lotus (Nelumbo nucifera Gaertn.) Rhizomes

“…During the development of lotus, most of the genes related to starch synthesis are expressed actively. [ 5 , 32 ]. SUS and SS were involved in the changes at development stages of lotus rhizome [ 26 ].…”

“…According to the fluorescence value measured by the double reporting system, the fluorescence value of the target gene plasmid the fluorescence value of the internal reference plasmid (F/R value) was calculated, and the ratio of the target gene plasmid to the control group was calculated, the standard error was calculated with SPSS software and the histogram was made with GraphPad Prism 8.0 software. Total RNA extraction from tobacco leaves and real-time qRT-PCR analysis of the Nnu miR396a-LUC, Nnu miR396b-LUC, NnSS2 -LUC and NnPGM2 -LUC were performed [ 32 , 48 ]. Three replicates were performed for each amplification reaction.…”

EfABI4 Transcription Factor Is Involved in the Regulation of Starch Biosynthesis in Euryale ferox Salisb Seeds

“…ZmABI4 can up-regulate the expression of ZmSS1 and ZmGBSS1 genes and increase the starch content in maize endosperm [ 35 ]. In addition, it was recently reported that NnABI4 in Nelumbo nucifera can directly bind to the promoter of NnSS1 and up-regulate its expression, ultimately promoting starch synthesis in rhizomes [ 11 ]. AtABI4 drives the expression of downstream genes by binding to the CE1-like motif element in the promoter region of the sugar response gene, such as the large subunit ApL3 of ADP-glucose pyrophosphorylase and the starch branch enzyme SBE2.2 in the starch synthesis pathway [ 53 ].…”

“…In addition, there was a positive correlation between ABA content and starch accumulation rate in seeds of wheat and barley at the grain filling stage [ 9 ]. Furthermore, exogenous ABA treatment can increase the starch content of banana [ 10 ], lotus [ 11 ], blueberry and peach [ 12 , 13 ]. However, the mechanism of ABA regulation of starch synthesis is unclear.…”

“…ABI4 regulates the expression of starch synthesis-related genes APL3 and SBE2 , and starch degradation genes SEX1 and BMY8/BAM3 , thus affecting the synthesis and accumulation of starch [ 34 ]. In addition, NnABI4 can activate and up-regulate the expression of NnSS1 , which promotes starch synthesis in Nelumbo nucifera [ 11 ]. Moreover, in maize endosperm, overexpressed ZmABI4 can also up-regulate the expression of AGPL2 , AGPLS4 , Sh2 , SS1 , GBSS1 , SBE2a , SBE2b and PHOL genes encoding AGPase, thus increasing starch content in maize endosperm [ 35 ].…”