## 1 Introduction  
Among the 750 Pandanus species, _Pandanus anaryllifolius_ is the only species that produces the major basmati aroma compound 2-acetyl-1-pyrroline (2 AP) in leaves. The species accumulates 2 AP at the highest concentrations reported in the plant kingdom [1; 2; 3]. Leaves of _P. anaryllifolius_ areroutinely used to flavor different food dishes in Southeast Asia [4]. In India, it was introduced in 1798, through the Botanical garden of Kolkata [5] and popularly cultivated along the Indian peninsular in kitchen gardens as a spice.  
This species has been extensively studied in the laboratory of AN as follows. Bag-like structures called epidermal papillae were identified on the lower epidermis of the leaves of this species and act as a site of storage for 2 AP [6]. Their pattern of development has been studied in the in vitro raised seedlings that showed that stomata act as the epicenter for its development [7]. A total of 21 new volatiles in this species have been identified [8]. Further, in vitro regeneration protocol has also been standardized. The populations of _P. anaryllifolius_ grown under a wide range of environmental conditions across the Indian peninsular regions were collected and an elite population with the highest 2 AP contents (12.2 ppm) was identified [9].These populations displayed remarkable genetic similarity.  
We now report an investigation of the molecular basis of the extreme 2 AP accumulation in this species. In aromatic rice and other plant species, 2 AP synthesis is correlated with the presence of a nonfunctional _BADH2_ gene [10]. A mutation in the _BADH2_ gene introducing a premature stop codon causes loss of gene function and starts accumulating GAB-ald, a substrate of BADH2, and this GAB-ald spontaneously reacts with methylglyoxal to produce 2 AP [11]. [PERSON] et al. [12] reported that _BADH2_ is playing a crucial role in maintaining the yield under salt stress and under exposure to stress conditions fragrant rice varieties with nonfunctional _BADH2_ is more susceptible to yield loss. A detailed understanding of the enzymatic and molecular mechanism of _BADH2_ in Pandanus can help to resolve the issue of stress susceptibility in fragrant rice. The BADH2 enzyme belongs to the aldehyde dehydrogenase (ALDH) super family. Members of this family possess substrate-binding, NAD\({}^{+}\)-binding, and oligomerization domains. The total loss of activity was observed associated with a mutation in Cys294 to alanine in the catalytic site of BADH2 [13; 14; 15]. Similarly, loss of activity was reported with a Glu260 to alanine mutation, and a reduced enzyme affinity was observed with an Asn162 to alanine mutation. Numerous studies have been carried out to identify the precursors of 2 AP in various plant species. These studies reported that proline, ornithine, and glutamate act as the primary precursors of 2 AP synthesis in _P. amarylifolius_[16; 17] and rice [18; 19].  
Although the economic importance of _P. amarylifolius_ is attributed to the aroma, limited information is available regarding the structure and specificity of BADH2 in this species. An earlier report [20] showed the presence of a truncated allelic form of the _BADH2_ gene in in vitro plantlets of _P. amarylifolius_ (PND BADH2, gene ID: KY765936.1). Furthermore, in silico analysis suggested that insufficient affinity between the PaBADH2 enzyme and its substrate GAB-ald might be the major determinant of aroma development in _P. amarylifolius_. Here, we obtained the full-length functional _PaBADH2_ sequence from the transcriptome analysis and characterized its enzymatic activity, gene expression, protein sequence, active site, and interaction with a substrate.