Importantly, it has been reported that GSO1/SGN3 is expressed in root endodermal cells and its loss-of-function mutations result in the formation of a repeatedly interrupted, discontinuous Casparian strip. These findings indicated that these two sulfated peptides act as ligands for GSO1/ SGN3 and GSO2 receptors to regulate contiguous Casparian strip formation in roots.
We confirmed that the double mutant devoid of these two peptide genes was a phenocopy of the receptor mutant, and external application of the synthetic peptides restored contiguous Casparian strip formation in the mutant roots.
Until recently, little was known about the genes that drive the formation of the Casparian strip
, which is composed of a fine band of lignin, the polymer that gives wood its strength.
Lyshede speculated that this cell layer, which does not develop a casparian strip
, transfers material from dying cortical and epidermal cells to the stele while at the same time resisting collapse in order to maintain the normal turgor of sieve tubes in the phloem.
sprucei, with vascular tissues centered and surrounded by an endodermis with Casparian strips
, with the xylem seen in transversal section as an open V of long arms, at the end of which a small amount of phloem is formed, a type also found in B.
The root primary growth (Figure 3A and B) shows irregular epidermis with thin-wall cells and unicellular hairs; cortex with unilateral or bisseriate exodermis of suberized wall cells, loose parenchymatic tissue with secretory ducts, and endodermis with Casparian strips
; and central cylinder with parenchymatous uniseriate pericycle, phloem strands alternating with an equal number of xylem strands, provided with six to ten protoxylematic poles (polyarcroot) and parenchymatous pith.
graminea, pluriseriate parenchyma and endodermis with Casparian strips
. Central cylinder is composed of uniseriate parenchymatous pericycle and three strands of primary xylem and phloem (Figure 2A and B).