Day-neutral response of photoperiodic flowering in tomatoes: Possible implications based on recent molecular genetics of Arabidopsis and rice

Abstract

Photoperiodic flowering responses are classified into three major types: long day (LD), short day (SD), and day neutral (DN). Arabidopsis is one of the best-characterized LD plants and flowers much earlier under LD than SD conditions. In contrast, SD conditions promote flowering of SD plants such as rice and Pharbitis nil. Recently, molecular genetics of Arabidopsis (LD) and rice (SD) have identified genes that play key roles in the photoperiodic flowering of these plants. A common role of the GIGANTEA (GI)-CONSTANS (CO)-FLOWERING LOCUS T (FT) pathway in Arabidopsis and rice, and a specific role of EARLY HEADING DATE 1 (EHD1) in rice, but not in Arabidopsis, have been demonstrated. The DN response is the most poorly characterized among the three types of photoperiodic flowering responses. In this short review, we discuss how the DN flowering response is achieved in tomato based on recent progress in the analysis of Arabidopsis mutations in the photoperiodic flowering pathway and circadian rhythms.