Abstract
Coconut palm has two distinct types—“tall” and “dwarf”—which differ morphologically. Tall coconut varieties need 8–10 years to start flowering, while dwarf coconut varieties only require 3–5 years. We compared seedling and reproductive stage transcriptomes for both coconut types to determine potential molecular mechanisms underlying control of flowering time in coconut. Several key genes in the photoperiod pathway were differentially expressed between seedling and reproductive leaf samples in both tall and dwarf coconut. These genes included suppressor of overexpression of constans (SOC1), flowering locus T (FT), and Apetala 1 (AP1). Alternative splicing analysis of genes in the photoperiod pathway further revealed that the FT gene produces different transcripts in tall compared to dwarf coconut. The shorter alternative splice variant of FT [which included a 6 bp deletion, alternative 3′ splicing sites (A3SS)] was found to be exclusively present in dwarf coconut varieties but absent in most tall coconut varieties. Our results provide a valuable information resource as well as suggesting a probable mechanism for differentiation of flowering time onset in coconut, providing a target for future breeding work in accelerating time to flowering in this crop species.
Highlights
Coconut palm has two distinct types—“tall” and “dwarf”—which differ morphologically
A total of five Flowering Locus T (FT)-like genes were found, of which HvFT1 was highly expressed under long-day conditions in transition from vegetative to reproductive growth, HvFT3 was identified as a candidate gene under a major flowering-time QTL, HvFT2 and HvFT4 were highly expressed at later developmental stages and HvFT5 showed low expression level under short-day c onditions[24]; highlighting the possible complexity of regulatory mechanisms involving multiple FT copies
Coconut can be subdivided into two types according to morphological characteristics: tall coconuts, which flower in 8–10 years, and dwarf coconut, which only need 3–5 years to flower[36]
Summary
Coconut palm has two distinct types—“tall” and “dwarf”—which differ morphologically. Tall coconut varieties need 8–10 years to start flowering, while dwarf coconut varieties only require 3–5 years. Several key genes in the photoperiod pathway were differentially expressed between seedling and reproductive leaf samples in both tall and dwarf coconut. These genes included suppressor of overexpression of constans (SOC1), flowering locus T (FT), and Apetala 1 (AP1). A total of five FT-like genes were found, of which HvFT1 was highly expressed under long-day conditions in transition from vegetative to reproductive growth, HvFT3 was identified as a candidate gene under a major flowering-time QTL, HvFT2 and HvFT4 were highly expressed at later developmental stages and HvFT5 showed low expression level under short-day c onditions[24]; highlighting the possible complexity of regulatory mechanisms involving multiple FT copies. A total of four FT-like genes were isolated in poplar, only one (PtFT2) was shown to shorten juvenile phase and promote seasonal flowering[28]
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