A molecular and structural characterization of senescing Arabidopsis siliques and comparison of transcriptional profiles with senescing petals and leaves

Abstract

SummarySenescence of plant organs is a genetically controlled process that regulates cell death to facilitate nutrient recovery and recycling, and frequently precedes, or is concomitant with, ripening of reproductive structures. In Arabidopsis thaliana, the seeds are contained within a silique, which is itself a photosynthetic organ in the early stages of development and undergoes a programme of senescence prior to dehiscence. A transcriptional analysis of the silique wall was undertaken to identify changes in gene expression during senescence and to correlate these events with ultrastructural changes. The study revealed that the most highly up-regulated genes in senescing silique wall tissues encoded seed storage proteins, and the significance of this finding is discussed. Global transcription profiles of senescing siliques were compared with those from senescing Arabidopsis leaf or petal tissues using microarray datasets and metabolic pathway analysis software (MapMan). In all three tissues, members of NAC and WRKY transcription factor families were up-regulated, but components of the shikimate and cell-wall biosynthetic pathways were down-regulated during senescence. Expression of genes encoding ethylene biosynthesis and action showed more similarity between senescing siliques and petals than between senescing siliques and leaves. Genes involved in autophagy were highly expressed in the late stages of death of all plant tissues studied, but not always during the preceding remobilization phase of senescence. Analyses showed that, during senescence, silique wall tissues exhibited more transcriptional features in common with petals than with leaves. The shared and distinct regulatory events associated with senescence in the three organs are evaluated and discussed.

Comprehensive Dissection of Spatiotemporal Metabolic Shifts in Primary, Secondary, and Lipid Metabolism during Developmental Senescence in Arabidopsis

“…6A), siliques with developing seeds as sinks display a distinctively different metabolite composition than leaves, corroborating their specific physiological program. Similarly, Wagstaff et al (2009) reported that even the silique wall, which is a photosynthetic organ during early stages of development, shows transcriptional features during senescence different from those in senescing leaves (Wagstaff et al, 2009). Thus, both studies reveal features unique to senescence occurring in siliques compared with senescence in rosette leaves.…”

Living to Die and Dying to Live: The Survival Strategy behind Leaf Senescence

“…Moreover, in many Brassica spp. crops, the photosynthetic stem and pod walls provide nutrients for developing seeds (Malagoli et al, 2005), reducing the requirement for leaf N remobilization during seed production (Wagstaff et al, 2009). Indeed, the stems of B. napus appear to act as transient storage organs when there is a mismatch between N demand by the seeds and the degree of leaf N remobilization (Girondé et al, 2015), which may be a consequence of the weedy traits that remain within leafy Brassica spp.…”

Development of a Statistical Crop Model to Explain the Relationship between Seed Yield and Phenotypic Diversity within the Brassica napus Genepool

“…However, the relationship between senescence and yield is a complex one and not fully understood [24], especially in oilseed rape. The role of the pod wall extends far beyond that of a protective organ [18,25], as the pods are themselves photosynthetic units that senesce, contributing 50%-60% of the final dry mass of the mature plant [26]. It has been noted that Arabidopsis accessions that naturally senesce early have a greater number of pods per plant compared to late-senescing accessions (although the nutritional composition and weight of these seeds were not stated), indicating a greater investment in reproductive as opposed to vegetative development [22,23].…”