Molecular cloning and functional analysis of phytochrome genes in photoperiod-sensitive soybean

Abstract:

Here is a practical dilemma that soybean breeders in tropical India face every season: cultivars bred for one latitude often flower too early or too late when moved just 3–4 degrees north or south, because their phytochrome-mediated photoperiod response is tuned to the original environment. This research cloned and functionally analysed four phytochrome genes (GmPhyA1, GmPhyA2, GmPhyB1, GmPhyB2) from the photoperiod-sensitive soybean cultivar JS 335 at Swarnim Gujarat Agricultural University, Gandhinagar. Full-length cDNA sequences were obtained by RT-PCR and confirmed by sequencing. Expression analysis under controlled short-day (10 h) and long-day (16 h) photoperiods showed that GmPhyA1 was the most strongly photoperiod-responsive gene, with 2.76-fold higher expression under short days. GmPhyB1 showed the opposite pattern, with 1.18-fold higher expression under long days. Transient overexpression of GmPhyA1 in Arabidopsis accelerated flowering by 4.2 days under short-day conditions. These results confirm that GmPhyA1 is a key regulator of short-day flowering induction in soybean and a candidate for molecular breeding of photoperiod-insensitive cultivars.