Light-regulated overexpression of an Arabidopsis phytochrome A gene in rice alters plant architecture and increases grain yield

Abstract

The phytochromes are a family of red/far-red light absorbing photoreceptors that control plant developmental and metabolic processes in response to changes in the light environment. We report here the overexpression of Arabidopsis thaliana PHYTOCHROME A (PHYA) gene in a commercially important indica rice variety (Oryza sativa L. Pusa Basmati-1). The expression of the transgene was driven by the light-regulated and tissue-specific rice rbcS promoter. Several independent homozygous sixth generation (T(5)) transgenic lines were characterized and shown to accumulate relatively high levels of PHYA protein in the light. Under both far-red and red light, PHYA-overexpressing lines showed inhibition of the coleoptile extension in comparison to non-transgenic seedlings. Furthermore, compared with non-transgenic rice plants, mature transgenic plants showed significant reduction in plant height, internode length and internode diameter (including differences in cell size and number), and produced an increased number of panicles per plant. Under greenhouse conditions, rice grain yield was 6-21% higher in three PHYA-overexpressing lines than in non-transgenic plants. These results demonstrate the potential of manipulating light signal-transduction pathways to minimize the problems of lodging in basmati/aromatic rice and to enhance grain productivity.

The Light-Response BTB1 and BTB2 Proteins Assemble Nuclear Ubiquitin Ligases That Modify Phytochrome B and D Signaling in Arabidopsis

“…Whereas increasing phy levels through transgenic expression has been offered as a mechanism to manipulate agronomically important processes controlled by these photoreceptors (e.g. seed germination and yield, shade avoidance, and flowering time; Garg et al, 2006;Boccalandro et al, 2009), we propose that manipulating the action of BTB LRB1/2 might offer an alternative route, at least for phyB/D-mediated photoresponses.…”

Plant pigments: the many faces of light perception

“…This is in part because the phytochromes have been known longer in comparison to other photoreceptors, and gene constructs to overexpress this photoreceptor family have been available for a long time. Phytochrome overexpressors have been shown to display strong phenotypes, many of which are desirable from the perspective of yield, harvesting time or plant architecture (Boccalandro et al 2003;Garg et al 2006). Furthermore, the availability of phytochrome mutants in different species has become a powerful tool in the studies of the effects of these photoreceptors.…”

Photoreceptor Biotechnology

“…Such a tool has obvious potential for agronomic application. A recent example of such an approach is the dwarfing of aromatic rice varieties by overexpression of Arabidopsis phyA (Garg et al, 2005). Details of this and other applications of photoreceptor-mediated dwarfing are given in Section III.…”

“…The effect of oat phyA overexpression in rice or wheat is marginal (Clough et al, 1995, Schlumukhov et al, 2003. Conversely, the introduction of an Arabidopsis PHYA gene into rice causes significant dwarfing and the promise of substantial increase in yield (Garg et al, 2005). A likely explanation for this observation is that the feedback controls acting post-transcriptionally on the native phytochromes (especially phyA) are not able to control introduced phytochrome genes as tightly.…”

“…However, improved transformation technologies have led to phytochrome overexpression being applied in rice (Clough et al, 1995, Garg et al, 2005 and wheat (Schlumukhov et al, 2003).…”